The Enzyme Database

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EC 5.1.1.1     
Accepted name: alanine racemase
Reaction: L-alanine = D-alanine
Other name(s): L-alanine racemase
Systematic name: alanine racemase
Comments: A pyridoxal-phosphate protein.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9024-06-0
References:
1.  Marr, A.G. and Wilson, P.W. The alanine racemase of Brucella abortus. Arch. Biochem. Biophys. 49 (1954) 424–433. [PMID: 13159289]
2.  Wood, W.A. Amino acid racemases. Methods Enzymol. 2 (1955) 212–217.
3.  Wood, W.A. and Gunsalus, I.C. D-Alanine formation: a racemase in Streptococcus faecalis. J. Biol. Chem. 190 (1951) 403–416. [PMID: 14841188]
[EC 5.1.1.1 created 1961]
 
 
EC 5.1.1.2     
Accepted name: methionine racemase
Reaction: L-methionine = D-methionine
Systematic name: methionine racemase
Comments: A pyridoxal-phosphate protein.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9024-07-1
References:
1.  Kallio, R.E. and Larson, A.D. Methionine degradation by a species of Pseudomonas. In: McElroy, W.D. and Glass, H.B. (Eds), A Symposium on Amino Acid Metabolism, Johns Hopkins Press, Baltimore, 1955, pp. 616–634.
[EC 5.1.1.2 created 1961]
 
 
EC 5.1.1.3     
Accepted name: glutamate racemase
Reaction: L-glutamate = D-glutamate
Systematic name: glutamate racemase
Comments: A pyridoxal-phosphate protein.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9024-08-2
References:
1.  Glaser, L. Glutamic acid racemase from Lactobacillus arabinosus. J. Biol. Chem. 235 (1960) 2095–2098. [PMID: 13828348]
[EC 5.1.1.3 created 1961]
 
 
EC 5.1.1.4     
Accepted name: proline racemase
Reaction: L-proline = D-proline
Systematic name: proline racemase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9024-09-3
References:
1.  Stadtman, T.C. and Elliott, P. Studies on the enzymic reduction of amino acids. II. Purification and properties of a D-proline reductase and a proline racemase from Clostridium sticklandii. J. Biol. Chem. 228 (1957) 983–997. [PMID: 13475375]
[EC 5.1.1.4 created 1961]
 
 
EC 5.1.1.5     
Accepted name: lysine racemase
Reaction: L-lysine = D-lysine
Systematic name: lysine racemase
Comments: The enzyme is involved in a lysine catabolic pathway.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, CAS registry number: 9024-10-6
References:
1.  Huang, H.T. and Davisson, J.W. Distribution of lysine racemase in bacteria. J. Bacteriol. 76 (1958) 495–498. [PMID: 13598707]
2.  Huang, H.T. dl-Lysine production by lysine racemase. Patent US2944943, 1960, Chem. Abstr., 54 (1960), 20073 (PDF).
3.  Chen, I.C., Lin, W.D., Hsu, S.K., Thiruvengadam, V. and Hsu, W.H. Isolation and characterization of a novel lysine racemase from a soil metagenomic library. Appl. Environ. Microbiol. 75 (2009) 5161–5166. [PMID: 19502445]
4.  Kato, S., Hemmi, H. and Yoshimura, T. Lysine racemase from a lactic acid bacterium, Oenococcus oeni: structural basis of substrate specificity. J. Biochem. 152 (2012) 505–508. [PMID: 23035128]
[EC 5.1.1.5 created 1961]
 
 
EC 5.1.1.6     
Accepted name: threonine racemase
Reaction: L-threonine = D-threonine
Glossary: D-threonine = (2R,3S)-2-amino-3-hydroxybutanoic acid
Systematic name: threonine racemase
Comments: Inverts both chiral centres.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9024-11-7
References:
1.  Amos, H. A racemase for threonine in Escherichia coli. J. Am. Chem. Soc. 76 (1954) 3858.
[EC 5.1.1.6 created 1961, modified 1981]
 
 
EC 5.1.1.7     
Accepted name: diaminopimelate epimerase
Reaction: LL-2,6-diaminoheptanedioate = meso-diaminoheptanedioate
Systematic name: LL-2,6-diaminoheptanedioate 2-epimerase
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9024-22-0
References:
1.  Antia, M., Hoare, D.S. and Work, W. The stereoisomers of αε-diaminopimelic acid. 3. Properties and distribution of diaminopimelic acid racemase, an enzyme causing interconversion of the LL and meso isomers. Biochem. J. 65 (1957) 448–459. [PMID: 13412646]
[EC 5.1.1.7 created 1961]
 
 
EC 5.1.1.8     
Accepted name: 4-hydroxyproline epimerase
Reaction: trans-4-hydroxy-L-proline = cis-4-hydroxy-D-proline
For diagram of reaction, click here
Other name(s): hydroxyproline epimerase; hydroxyproline 2-epimerase; L-hydroxyproline epimerase
Systematic name: 4-hydroxyproline 2-epimerase
Comments: Also interconverts trans-4-hydroxy-D-proline and cis-4-hydroxy-L-proline.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, CAS registry number: 9024-23-1
References:
1.  Adams, E. and Norton, I.L. Purification and properties of inducible hydroxyproline 2-epimerase from Pseudomonas. J. Biol. Chem. 239 (1964) 1525–1535. [PMID: 14189888]
[EC 5.1.1.8 created 1965, modified 1983]
 
 
EC 5.1.1.9     
Accepted name: arginine racemase
Reaction: L-arginine = D-arginine
Systematic name: arginine racemase
Comments: A pyridoxal-phosphate protein.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37290-94-1
References:
1.  Yorifuji, T., Ogata, K. and Soda, K. Crystalline arginine racemase. Biochem. Biophys. Res. Commun. 34 (1969) 760–764. [PMID: 5779761]
[EC 5.1.1.9 created 1972]
 
 
EC 5.1.1.10     
Accepted name: amino-acid racemase
Reaction: an L-amino acid = a D-amino acid
Other name(s): L-amino acid racemase
Systematic name: amino-acid racemase
Comments: A pyridoxal-phosphate protein.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9068-61-5
References:
1.  Soda, K. and Osumi, T. Crystalline amino acid racemase with low substrate specificity. Biochem. Biophys. Res. Commun. 35 (1969) 363–368. [PMID: 5788493]
[EC 5.1.1.10 created 1972]
 
 
EC 5.1.1.11     
Accepted name: phenylalanine racemase (ATP-hydrolysing)
Reaction: ATP + L-phenylalanine + H2O = AMP + diphosphate + D-phenylalanine
Other name(s): phenylalanine racemase; phenylalanine racemase (adenosine triphosphate-hydrolysing); gramicidin S synthetase I
Systematic name: phenylalanine racemase (ATP-hydrolysing)
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37290-95-2
References:
1.  Yamada, M. and Kurahashi, K. Further purification and properties of adenosine triphosphate-dependent phenylalanine racemase of Bacillus brevis Nagano. J. Biochem. (Tokyo) 66 (1969) 529–540. [PMID: 5354026]
[EC 5.1.1.11 created 1972]
 
 
EC 5.1.1.12     
Accepted name: ornithine racemase
Reaction: L-ornithine = D-ornithine
Systematic name: ornithine racemase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 62213-28-9
References:
1.  Chen, H.P., Lin, C.F., Lee, Y.J., Tsay, S.S. and Wu, S.H. Purification and properties of ornithine racemase from Clostridium sticklandii. J. Bacteriol. 182 (2000) 2052–2054. [PMID: 10715017]
[EC 5.1.1.12 created 1972 as EC 5.4.3.1, transferred 1976 to EC 5.1.1.12]
 
 
EC 5.1.1.13     
Accepted name: aspartate racemase
Reaction: L-aspartate = D-aspartate
Other name(s): D-aspartate racemase; McyF
Systematic name: aspartate racemase
Comments: Also acts, at half the rate, on L-alanine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37237-56-2
References:
1.  Lamont, H.C., Staudenbauer, W.L. and Strominger, J.L. Partial purification and characterization of an aspartate racemase from Streptococcus faecalis. J. Biol. Chem. 247 (1972) 5103–5106. [PMID: 4626916]
2.  Yamauchi, T., Choi, S.Y., Okada, H., Yohda, M., Kumagai, H., Esaki, N. and Soda, K. Properties of aspartate racemase, a pyridoxal 5′-phosphate-independent amino acid racemase. J. Biol. Chem. 267 (1992) 18361–18364. [PMID: 1526977]
3.  Liu, L., Iwata, K., Kita, A., Kawarabayasi, Y., Yohda, M. and Miki, K. Crystal structure of aspartate racemase from Pyrococcus horikoshii OT3 and its implications for molecular mechanism of PLP-independent racemization. J. Mol. Biol. 319 (2002) 479–489. [PMID: 12051922]
4.  Sielaff, H., Dittmann, E., Tandeau De Marsac, N., Bouchier, C., von Döhren, H., Börner, T. and Schwecke, T. The mcyF gene of the microcystin biosynthetic gene cluster from Microcystis aeruginosa encodes an aspartate racemase. Biochem. J. 373 (2003) 909–916. [PMID: 12713441]
5.  Yamashita, T., Ashiuchi, M., Ohnishi, K., Kato, S., Nagata, S. and Misono, H. Molecular identification of monomeric aspartate racemase from Bifidobacterium bifidum. Eur. J. Biochem. 271 (2004) 4798–4803. [PMID: 15606767]
[EC 5.1.1.13 created 1976]
 
 
EC 5.1.1.14     
Accepted name: nocardicin A epimerase
Reaction: (1) isonocardicin C = nocardicin C
(2) isonocardicin A = nocardicin A
For diagram of nocardicin biosynthesis, click here and for diagram of nocardicin A biosynthesis, click here
Glossary: nocardicin A = (2R)-2-amino-4-{4-[(1E)-{[(3S)-1-[(R)-carboxy(4-hydroxyphenyl)methyl]-2-oxoazetidin-3-yl]carbamoyl}(hydroxyimino)methyl]phenoxy}butanoic acid
isonocardicin A =(2S)-2-amino-4-{4-[(1E)-{[(3S)-1-[(R)-carboxy(4-hydroxyphenyl)methyl]-2-oxoazetidin-3-yl]carbamoyl}(hydroxyimino)methyl]phenoxy}butanoic acid
nocardicin C = (2R)-2-amino-4-{4-[(R)-amino({[(3S)-1-[(R)-carboxy(4-hydroxyphenyl)methyl]-2-oxoazetidin-3-yl]carbamoyl})methyl]phenoxy}butanoic acid
isonocardicin C = (2S)-2-amino-4-{4-[(R)-amino({[(3S)-1-[(R)-carboxy(4-hydroxyphenyl)methyl]-2-oxoazetidin-3-yl]carbamoyl})methyl]phenoxy}butanoic acid
Other name(s): isonocardicin A epimerase; nocJ (gene name)
Systematic name: nocardicin-C epimerase
Comments: Requires pyridoxal 5′-phosphate. The enzyme, characterized from the bacterium Nocardia uniformis, is involved in the biosynthesis of the monolactam antibiotic nocardicin A. It catalyses the epimerization of the amino group at position 9′ from (S)- configuration to (R)-. The enzyme can act on both isonocardicin A and isonocardicin C, but the in vivo substrate appears to be the latter [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 118246-75-6
References:
1.  Wilson, B.A., Bantia, S., Salituro, G.M., Reeve, A.M. and Townsend, C.A. Cell-free biosynthesis of nocardicin A from nocardicin E and S-adenosylmethionine. J. Am. Chem. Soc. 110 (1988) 8238–8239.
2.  Kelly, W.L. and Townsend, C.A. Mutational analysis and characterization of nocardicin C-9′ epimerase. J. Biol. Chem. 279 (2004) 38220–38227. [PMID: 15252031]
3.  Kelly, W.L. and Townsend, C.A. Mutational analysis of nocK and nocL in the nocardicin a producer Nocardia uniformis. J. Bacteriol. 187 (2005) 739–746. [PMID: 15629944]
[EC 5.1.1.14 created 1992, modified 2016]
 
 
EC 5.1.1.15     
Accepted name: 2-aminohexano-6-lactam racemase
Reaction: (S)-2-aminohexano-6-lactam = (R)-2-aminohexano-6-lactam
Glossary: (S)-2-aminohexano-6-lactam = L-lysine 1,6-lactam
Other name(s): α-amino-ε-caprolactam racemase
Systematic name: 2-aminohexano-6-lactam racemase
Comments: Contains pyridoxal 5′-phosphate. Also racemises 2-aminopentano-5-lactam (α-amino-δ-valerolactam) and 2-amino-4-thiahexano-6-lactam (where S replaces CH2 of C-4). It does not catalyse the racemisation of α-amino acids but has some transaminase activity with them.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 52652-64-9
References:
1.  Ahmed, S.A., Esaki, N., Tanaka, H., Soda, K. L-α-Amino-β-thio-ε-caprolactam, a new sulfur-containing substrate for α-amino-ε-caprolactam racemase. FEBS Lett. 174 (1984) 76–79.
2.  Ahmed, S.A., Esaki, N., Tanaka, H., Soda, K. Mechanism of α-amino-ε-caprolactam racemase reaction. Biochemistry 25 (1986) 385–388. [PMID: 3955003]
3.  Okazaki, S., Suzuki, A., Mizushima, T., Kawano, T., Komeda, H., Asano, Y. and Yamane, T. The novel structure of a pyridoxal 5′-phosphate-dependent fold-type I racemase, α-amino-ε-caprolactam racemase from Achromobacter obae. Biochemistry 48 (2009) 941–950. [PMID: 19146406]
[EC 5.1.1.15 created 1999]
 
 
EC 5.1.1.16     
Accepted name: protein-serine epimerase
Reaction: [protein]-L-serine = [protein]-D-serine
Other name(s): protein-serine racemase
Systematic name: [protein]-serine epimerase
Comments: The enzyme specifically interconverts the configuration of Ser-46 of the peptide ω-agatoxin-KT, found in the venom of the funnel web spider, Agelenopsis aperta, but not that of the other serine residue, Ser-28.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 169592-52-3
References:
1.  Shikata, Y., Watanabe, T., Teramoto, T., Inoue, A., Kawakami, Y., Nishizawa, Y., Katayama, K., Kuwada, M. Isolation and characterization of a peptide isomerase from funnel web spider venom. J. Biol. Chem. 270 (1995) 16719–16723. [PMID: 7622482]
[EC 5.1.1.16 created 1999]
 
 
EC 5.1.1.17     
Accepted name: isopenicillin-N epimerase
Reaction: isopenicillin N = penicillin N
For diagram of penicillin-N and deacetoxycephalosporin-C biosynthesis, click here
Systematic name: penicillin-N 5-amino-5-carboxypentanoyl-epimerase
Comments: This enzyme contains pyridoxal phosphate. Epimerization at C-5 of the 5-amino-5-carboxypentanoyl group to form penicillin N is required to make a substrate for EC 1.14.20.1, deactoxycephalosporin-C synthase, to produce cephalosporins. Forms part of the penicillin biosynthesis pathway (for pathway, click here).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 88201-43-8
References:
1.  Usui, S. and Yu, C.-A. Purification and properties of isopenicillin-N epimerase from Streptomyces clavuligerus. Biochim. Biophys. Acta 999 (1989) 78–85. [PMID: 2804141]
2.  Laiz, L., Liras, P., Castro, J.M. and Martín, J.F. Purification and characterization of the isopenicillin-N epimerase from Nocardia lactamdurans. J. Gen. Microbiol. 136 (1990) 663–671.
3.  Cantwell, C., Beckmann, R., Whiteman, P., Queener, S.W. and Abraham, E.P. Isolation of deacetoxycephalosporin-c from fermentation broths of Penicillium chrysogenum transformants - construction of a new fungal biosynthetic-pathway. Proc. R. Soc. Lond. B Biol. Sci. 248 (1992) 283–289. [PMID: 1354366]
4.  Yeh, W.K., Ghag, S.K. and Queener, S.W. Enzymes for epimerization of isopenicillin N, ring expansion of penicillin N, and 3′-hydroxylation of deacetoxycephalosporin C. Function, evolution, refolding, and enzyme engineering. Ann. N.Y. Acad. Sci. 672 (1992) 396–408.
[EC 5.1.1.17 created 2002]
 
 
EC 5.1.1.18     
Accepted name: serine racemase
Reaction: L-serine = D-serine
Other name(s): SRR
Systematic name: serine racemase
Comments: A pyridoxal-phosphate protein that is highly selective for L-serine as substrate. D-Serine is found in type-II astrocytes in mammalian brain, where it appears to be an endogenous ligand of the glycine site of N-methyl-D-aspartate (NMDA) receptors [1,2]. The reaction can also occur in the reverse direction but does so more slowly at physiological serine concentrations [4].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 77114-08-0
References:
1.  Wolosker, H., Blackshaw, S. and Snyder, S.H. Serine racemase: a glial enzyme synthesizing D-serine to regulate glutamate-N-methyl-D-aspartate neurotransmission. Proc. Natl. Acad. Sci. USA 96 (1999) 13409–13414. [PMID: 10557334]
2.  Wolosker, H., Sheth, K.N., Takahashi, M., Mothet, J.P., Brady, R.O., Jr., Ferris, C.D. and Snyder, S.H. Purification of serine racemase: biosynthesis of the neuromodulator D-serine. Proc. Natl. Acad. Sci. USA 96 (1999) 721–725. [PMID: 9892700]
3.  De Miranda, J., Santoro, A., Engelender, S. and Wolosker, H. Human serine racemase: moleular cloning, genomic organization and functional analysis. Gene 256 (2000) 183–188. [PMID: 11054547]
4.  Foltyn, V.N., Bendikov, I., De Miranda, J., Panizzutti, R., Dumin, E., Shleper, M., Li, P., Toney, M.D., Kartvelishvily, E. and Wolosker, H. Serine racemase modulates intracellular D-serine levels through an α,β-elimination activity. J. Biol. Chem. 280 (2005) 1754–1763. [PMID: 15536068]
[EC 5.1.1.18 created 2007]
 
 
EC 5.1.1.19     
Accepted name: O-ureido-serine racemase
Reaction: O-ureido-L-serine = O-ureido-D-serine
Glossary: O-ureido-L-serine = (2S)-2-amino-3-[(carbamoylamino)oxy]propanoate
O-ureido-D-serine = (2R)-2-amino-3-[(carbamoylamino)oxy]propanoate
Other name(s): dcsC (gene name)
Systematic name: (2S)-2-amino-3-[(carbamoylamino)oxy]propanoate 2-epimerase
Comments: The enzyme employs a two-base mechanism, with a thiolate-thiol pair in the active site. It participates in the biosynthetic pathway of D-cycloserine, an antibiotic substance produced by several Streptomyces species.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Kumagai, T., Koyama, Y., Oda, K., Noda, M., Matoba, Y. and Sugiyama, M. Molecular cloning and heterologous expression of a biosynthetic gene cluster for the antitubercular agent D-cycloserine produced by Streptomyces lavendulae. Antimicrob. Agents Chemother. 54 (2010) 1132–1139. [PMID: 20086163]
2.  Dietrich, D., van Belkum, M.J. and Vederas, J.C. Characterization of DcsC, a PLP-independent racemase involved in the biosynthesis of D-cycloserine. Org. Biomol. Chem. 10 (2012) 2248–2254. [PMID: 22307920]
[EC 5.1.1.19 created 2013]
 
 
EC 5.1.1.20     
Accepted name: L-Ala-D/L-Glu epimerase
Reaction: L-alanyl-D-glutamate = L-alanyl-L-glutamate
Other name(s): YkfB; YcjG; AEE; AE epimerase
Systematic name: L-alanyl-D-glutamate epimerase
Comments: The enzyme, characterized from the bacteria Escherichia coli and Bacillus subtilis, is involved in the recycling of the murein peptide, of which L-Ala-D-Glu is a component. In vitro the enzyme from Escherichia coli epimerizes several L-Ala-L-X dipeptides with broader specificity than the enzyme from Bacillus subtilis.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Schmidt, D.M., Hubbard, B.K. and Gerlt, J.A. Evolution of enzymatic activities in the enolase superfamily: functional assignment of unknown proteins in Bacillus subtilis and Escherichia coli as L-Ala-D/L-Glu epimerases. Biochemistry 40 (2001) 15707–15715. [PMID: 11747447]
2.  Gulick, A.M., Schmidt, D.M., Gerlt, J.A. and Rayment, I. Evolution of enzymatic activities in the enolase superfamily: crystal structures of the L-Ala-D/L-Glu epimerases from Escherichia coli and Bacillus subtilis. Biochemistry 40 (2001) 15716–15724. [PMID: 11747448]
[EC 5.1.1.20 created 2015]
 
 
EC 5.1.1.21     
Accepted name: isoleucine 2-epimerase
Reaction: L-isoleucine = D-allo-isoleucine
Other name(s): BCAA racemase
Systematic name: isoleucine 2-epimerase
Comments: A pyridoxal phosphate protein. The enzyme, characterized from the bacterium Lactobacillus buchneri, specifically catalyses racemization of nonpolar amino acids at the C-2 position.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Mutaguchi, Y., Ohmori, T., Wakamatsu, T., Doi, K. and Ohshima, T. Identification, purification, and characterization of a novel amino acid racemase, isoleucine 2-epimerase, from Lactobacillus species. J. Bacteriol. 195 (2013) 5207–5215. [PMID: 24039265]
[EC 5.1.1.21 created 2015]
 
 
EC 5.1.1.22     
Accepted name: 4-hydroxyproline betaine 2-epimerase
Reaction: (1) trans-4-hydroxy-L-proline betaine = cis-4-hydroxy-D-proline betaine
(2) L-proline betaine = D-proline betaine
Glossary: trans-4-hydroxy-L-proline betaine = (2S,4R)-4-hydroxy-1,1-dimethylpyrrolidinium-2-carboxylate
cis-4-hydroxy-D-proline betaine = (2R,4R)-4-hydroxy-1,1-dimethylpyrrolidinium-2-carboxylate
L-proline betaine = (2S)-1,1-dimethylpyrrolidinium-2-carboxylate
D-proline betaine = (2R)-1,1-dimethylpyrrolidinium-2-carboxylate
Other name(s): hpbD (gene name); Hyp-B 2-epimerase; (4R)-4-hydroxyproline betaine 2-epimerase
Systematic name: 4-hydroxyproline betaine 2-epimerase
Comments: The enzyme, characterized from the bacteria Pelagibaca bermudensis and Paracoccus denitrificans, specifically catalyses racemization of trans-4-hydroxy-L-proline betaine and L-proline betaine at the C-2 position.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Zhao, S., Kumar, R., Sakai, A., Vetting, M.W., Wood, B.M., Brown, S., Bonanno, J.B., Hillerich, B.S., Seidel, R.D., Babbitt, P.C., Almo, S.C., Sweedler, J.V., Gerlt, J.A., Cronan, J.E. and Jacobson, M.P. Discovery of new enzymes and metabolic pathways by using structure and genome context. Nature 502 (2013) 698–702. [PMID: 24056934]
2.  Kumar, R., Zhao, S., Vetting, M.W., Wood, B.M., Sakai, A., Cho, K., Solbiati, J., Almo, S.C., Sweedler, J.V., Jacobson, M.P., Gerlt, J.A. and Cronan, J.E. Prediction and biochemical demonstration of a catabolic pathway for the osmoprotectant proline betaine. MBio 5 (2014) e00933. [PMID: 24520058]
[EC 5.1.1.22 created 2017]
 
 
EC 5.1.2.1     
Accepted name: lactate racemase
Reaction: (S)-lactate = (R)-lactate
Other name(s): lacticoracemase; hydroxyacid racemase; lactic acid racemase; larA (gene name)
Systematic name: lactate racemase
Comments: The enzyme has been characterized from the bacterium Lactobacillus plantarum and appears to be restricted to lactic acid bacteria. It contains a unique nickel-containing cofactor, pyridinium-3-thioamide-5-thiocarboxylate mononucleotide Ni pincer complex.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9024-05-9
References:
1.  Huennekens, F.M., Mahler, H.R. and Nordmann, J. Studies on the cyclophorase system. XVII. The occurrence and properties of an α-hydroxy acid racemase. Arch. Biochem. 30 (1951) 77–89. [PMID: 14800428]
2.  Kitahara, K., Obayashi, A. and Fukui, S. Racemase I cell-free racemase. Enzymologia 15 (1953) 259–266.
3.  Goffin, P., Deghorain, M., Mainardi, J.L., Tytgat, I., Champomier-Verges, M.C., Kleerebezem, M. and Hols, P. Lactate racemization as a rescue pathway for supplying D-lactate to the cell wall biosynthesis machinery in Lactobacillus plantarum. J. Bacteriol. 187 (2005) 6750–6761. [PMID: 16166538]
4.  Desguin, B., Goffin, P., Viaene, E., Kleerebezem, M., Martin-Diaconescu, V., Maroney, M.J., Declercq, J.P., Soumillion, P. and Hols, P. Lactate racemase is a nickel-dependent enzyme activated by a widespread maturation system. Nat Commun 5:3615 (2014). [PMID: 24710389]
5.  Desguin, B., Zhang, T., Soumillion, P., Hols, P., Hu, J. and Hausinger, R.P. A tethered niacin-derived pincer complex with a nickel-carbon bond in lactate racemase. Science 349 (2015) 66–69. [PMID: 26138974]
6.  Yu, M.J. and Chen, S.L. From NAD+ to nickel pincer complex: a significant cofactor evolution presented by lactate racemase. Chemistry 23 (2017) 7545–7557. [PMID: 28374531]
[EC 5.1.2.1 created 1961]
 
 
EC 5.1.2.2     
Accepted name: mandelate racemase
Reaction: (S)-mandelate = (R)-mandelate
Glossary: mandelate = 2-hydroxy-2-phenylacetate
Systematic name: mandelate racemase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, UM-BBD, CAS registry number: 9024-04-8
References:
1.  Gunsalus, C.F., Stanier, R.Y. and Gunsalus, I.C. The enzymatic conversion of mandelic acid to benzoic acid. III. Fractionation and properties of the soluble enzymes. J. Bacteriol. 66 (1953) 548–553. [PMID: 13108854]
[EC 5.1.2.2 created 1961]
 
 
EC 5.1.2.3     
Accepted name: 3-hydroxybutyryl-CoA epimerase
Reaction: (S)-3-hydroxybutanoyl-CoA = (R)-3-hydroxybutanoyl-CoA
Other name(s): 3-hydroxybutyryl coenzyme A epimerase; 3-hydroxyacyl-CoA epimerase
Systematic name: 3-hydroxybutanoyl-CoA 3-epimerase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9024-21-9
References:
1.  Stern, J.R., del Campillo, A. and Lehninger, A.L. Enzymatic racemization of β-hydroxybutyryl-S-CoA and the stereospecificity of enzymes of the fatty acid cycle. J. Am. Chem. Soc. 77 (1955) 1073–1074.
2.  Wakil, S.J. D(-)β-Hydroxybutyryl CoA dehydrogenase. Biochim. Biophys. Acta 18 (1955) 314–315. [PMID: 13276396]
[EC 5.1.2.3 created 1961]
 
 
EC 5.1.2.4     
Accepted name: acetoin racemase
Reaction: (S)-acetoin = (R)-acetoin
Other name(s): acetylmethylcarbinol racemase
Systematic name: acetoin racemase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37318-32-4
References:
1.  Taylor, M.B. and Juni, E. Stereoisomeric specificities of 2,3-butanediol dehydrogenase. Biochim. Biophys. Acta 39 (1960) 448–457. [PMID: 13837186]
[EC 5.1.2.4 created 1972]
 
 
EC 5.1.2.5     
Accepted name: tartrate epimerase
Reaction: (R,R)-tartrate = meso-tartrate
Other name(s): tartaric racemase
Systematic name: tartrate epimerase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37318-33-5
References:
1.  Ranjan, S., Patnaik, K.K. and Laloraya, M.M. Enzymic conversion of meso-tartrate to dextro-tartrate in tamarind. Naturwissenschaften 48 (1961) 406.
[EC 5.1.2.5 created 1972]
 
 
EC 5.1.2.6     
Accepted name: isocitrate epimerase
Reaction: (1R,2S)-1-hydroxypropane-1,2,3-tricarboxylate = (1S,2S)-1-hydroxypropane-1,2,3-tricarboxylate
For diagram of reaction, click here
Glossary: isocitrate = (1R,2S)-1-hydroxypropane-1,2,3-tricarboxylate = threo-Ds-isocitrate
allocitrate = (1S,2S)-1-hydroxypropane-1,2,3-tricarboxylate = D-erythro-isocitrate
Systematic name: (1R,2S)-1-hydroxypropane-1,2,3-tricarboxylate 1-epimerase
Comments: (1R,2S)-1-hydroxypropane-1,2,3-tricarboxylate is the commonly occurring isomer of isocitrate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 81210-68-6
References:
1.  Hoshiko, S., Kunimoto, Y., Arima, K. and Beppu, T. Mechanism of L-alloisocitric acid fermentation: isocitrate epimerase activity in the cell-free-extract of Penicillium purpurogenum. Agric. Biol. Chem. 46 (1982) 143–151.
[EC 5.1.2.6 created 1984]
 
 
EC 5.1.2.7     
Accepted name: tagaturonate epimerase
Reaction: D-tagaturonate = D-fructuronate
Other name(s): fructuronate epimerase; tagaturonate/fructuronate epimerase; UxaE
Systematic name: D-tagaturonate 3-epimerase
Comments: The enzyme, present in bacteria, is involved in a degradation pathway of D-galacturonate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Rodionova, I.A., Scott, D.A., Grishin, N.V., Osterman, A.L. and Rodionov, D.A. Tagaturonate-fructuronate epimerase UxaE, a novel enzyme in the hexuronate catabolic network in Thermotoga maritima. Environ Microbiol 14 (2012) 2920–2934. [PMID: 22925190]
[EC 5.1.2.7 created 2017]
 
 
EC 5.1.3.1     
Accepted name: ribulose-phosphate 3-epimerase
Reaction: D-ribulose 5-phosphate = D-xylulose 5-phosphate
For diagram of the early stages of the pentose-phosphate pathway, click here and for diagram of the Calvin cycle, click here
Other name(s): phosphoribulose epimerase; erythrose-4-phosphate isomerase; phosphoketopentose 3-epimerase; xylulose phosphate 3-epimerase; phosphoketopentose epimerase; ribulose 5-phosphate 3-epimerase; D-ribulose phosphate-3-epimerase; D-ribulose 5-phosphate epimerase; D-ribulose-5-P 3-epimerase; D-xylulose-5-phosphate 3-epimerase; pentose-5-phosphate 3-epimerase
Systematic name: D-ribulose-5-phosphate 3-epimerase
Comments: The enzyme also converts D-erythrose 4-phosphate into D-erythrulose 4-phosphate and D-threose 4-phosphate.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9024-20-8
References:
1.  Ashwell, G. and Hickman, J. Enzymatic formation of xylulose 5-phosphate from ribose 5-phosphate in spleen. J. Biol. Chem. 226 (1957) 65–76. [PMID: 13428737]
2.  Dickens, F. and Williamson, D.H. Pentose phosphate isomerase and epimerase from animal tissues. Biochem. J. 64 (1956) 567–578. [PMID: 13373810]
3.  Hurwitz, J. and Horecker, B.L. The purification of phosphoketopentoepimerase from Lactobacillus pentosus and the preparation of xylulose 5-phosphate. J. Biol. Chem. 223 (1956) 993–1008. [PMID: 13385247]
4.  Stumpf, P.K. and Horecker, B.L. The røole of xylulose 5-phosphate in xylose metabolism of Lactobacillus pentosus. J. Biol. Chem. 218 (1956) 753–768. [PMID: 13295228]
5.  Terada, H., Mukae, K., Hosomi, S., Mizoguchi, T. and Uehara, K. Characterization of an enzyme which catalyzes isomerization and epimerization of D-erythrose 4-phosphate. Eur. J. Biochem. 148 (1985) 345–351. [PMID: 3987693]
[EC 5.1.3.1 created 1961, modified 1989]
 
 
EC 5.1.3.2     
Accepted name: UDP-glucose 4-epimerase
Reaction: UDP-α-D-glucose = UDP-α-D-galactose
For diagram of UDP-glucose, UDP-galactose and UDP-glucuronate biosynthesis, click here
Other name(s): UDP-galactose 4-epimerase; uridine diphosphoglucose epimerase; galactowaldenase; UDPG-4-epimerase; uridine diphosphate galactose 4-epimerase; uridine diphospho-galactose-4-epimerase; UDP-glucose epimerase; 4-epimerase; uridine diphosphoglucose 4-epimerase; uridine diphosphate glucose 4-epimerase; UDP-D-galactose 4-epimerase
Systematic name: UDP-α-D-glucose 4-epimerase
Comments: Requires NAD+. Also acts on UDP-2-deoxyglucose.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9032-89-7
References:
1.  Leloir, L.F. Enzymic isomerization and related processes. Adv. Enzymol. Relat. Subj. Biochem. 14 (1953) 193–218. [PMID: 13057717]
2.  Maxwell, E.S. and de Robichon-Szulmajster, H. Purification of uridine diphosphate galactose-4-epimerase from yeast and the identification of protein-bound diphosphopyridine nucleotide. J. Biol. Chem. 235 (1960) 308–312.
3.  Wilson, D.B. and Hogness, D.S. The enzymes of the galactose operon in Escherichia coli. I. Purification and characterization of uridine diphosphogalactose 4-epimerase. J. Biol. Chem. 239 (1964) 2469–2481. [PMID: 14235524]
[EC 5.1.3.2 created 1961]
 
 
EC 5.1.3.3     
Accepted name: aldose 1-epimerase
Reaction: α-D-glucose = β-D-glucose
Other name(s): mutarotase; aldose mutarotase; galactose mutarotase; galactose 1-epimerase; D-galactose 1-epimerase
Systematic name: aldose 1-epimerase
Comments: Also acts on L-arabinose, D-xylose, D-galactose, maltose and lactose. This enzyme catalyses the first step in galactose metabolism by converting β-D-galactose into α-D-galactose, which is the substrate for EC 2.7.1.6, galactokinase [5,6].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9031-76-9
References:
1.  Bentley, R. and Bhate, D.S. Mutarotase from Penicillium notatum. I. Purification, assay, and general properties of the enzyme. J. Biol. Chem. 235 (1960) 1219–1224. [PMID: 13799037]
2.  Bentley, R. and Bhate, D.S. Mutarotase from Penicillium notatum. II. The mechanism of the mutarotation reaction. J. Biol. Chem. 235 (1960) 1225–1233. [PMID: 13799038]
3.  Keilin, D. and Hartree, E.F. Biological catalysis of mutarotation of glucose. Biochem. J. 50 (1952) 341–348. [PMID: 14915955]
4.  Levy, G.B. and Cook, E.S. A rotographic study of mutarotase. Biochem. J. 57 (1954) 50–55. [PMID: 13159947]
5.  Beebe, J.A. and Frey, P.A. Galactose mutarotase: purification, characterization, and investigations of two important histidine residues. Biochemistry 37 (1998) 14989–14997. [PMID: 9778377]
6.  Thoden, J.B., Timson, D.J., Reece, R.J. and Holden, H.M. Molecular structure of human galactose mutarotase. J. Biol. Chem. 279 (2004) 23431–23437. [PMID: 15026423]
7.  Thoden, J.B., Kim, J., Raushel, F.M. and Holden, H.M. The catalytic mechanism of galactose mutarotase. Protein Sci. 12 (2003) 1051–1059. [PMID: 12717027]
[EC 5.1.3.3 created 1961]
 
 
EC 5.1.3.4     
Accepted name: L-ribulose-5-phosphate 4-epimerase
Reaction: L-ribulose 5-phosphate = D-xylulose 5-phosphate
For diagram of the bacterial pathway of ascorbic-acid catabolism, click here
Other name(s): phosphoribulose isomerase; ribulose phosphate 4-epimerase; L-ribulose-phosphate 4-epimerase; L-ribulose 5-phosphate 4-epimerase; AraD; L-Ru5P
Systematic name: L-ribulose-5-phosphate 4-epimerase
Comments: Requires a divalent cation for activity.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9024-19-5
References:
1.  Burma, D.P. and Horecker, B.L. IV. L-Ribulose-5-phosphate 4-epimerase. Pentose formation by Lactobacillus plantarum. J. Biol. Chem. 231 (1958) 1053–1064. [PMID: 13539036]
2.  Deupree, J.D. and Wood, W.A. L-Ribulose 5-phosphate 4-epimerase of Aerobacter aerogenes. Evidence for nicotinamide adenine dinucleotide-independent 4-epimerization by the crystalline enzyme. J. Biol. Chem. 245 (1970) 3988–3995. [PMID: 4395381]
3.  Lee, N., Patrick, J.W. and Masson, M. Crystalline L-ribulose 5-phosphate 4-epimerase from Escherichia coli. J. Biol. Chem. 243 (1968) 4700–4705. [PMID: 4879898]
4.  Wolin, M.J., Simpson, F.J. and Wood, W.A. Degradation of L-arabinose by Aerobacter aerogenes. III. Identification and properties of L-ribulose-5-phosphate 4-epimerase. J. Biol. Chem. 232 (1958) 559–575. [PMID: 13549442]
5.  Andersson, A., Schneider, G. and Lindqvist, Y. Purification and preliminary X-ray crystallographic studies of recombinant L-ribulose-5-phosphate 4-epimerase from Escherichia coli. Protein Sci. 4 (1995) 1648–1650. [PMID: 8520491]
6.  Lee, L.V., Poyner, R.R., Vu, M.V. and Cleland, W.W. Role of metal ions in the reaction catalyzed by L-ribulose-5-phosphate 4-epimerase. Biochemistry 39 (2000) 4821–4830. [PMID: 10769139]
7.  Samuel, J., Luo, Y., Morgan, P.M., Strynadka, N.C. and Tanner, M.E. Catalysis and binding in L-ribulose-5-phosphate 4-epimerase: a comparison with L-fuculose-1-phosphate aldolase. Biochemistry 40 (2001) 14772–14780. [PMID: 11732896]
[EC 5.1.3.4 created 1965, modified 2005]
 
 
EC 5.1.3.5     
Accepted name: UDP-arabinose 4-epimerase
Reaction: UDP-L-arabinose = UDP-D-xylose
For diagram of the biosynthesis of UDP-L-arabinose, UDP-galacturonate and UDP-xylose, click here
Other name(s): uridine diphosphoarabinose epimerase; UDP arabinose epimerase; uridine 5′-diphosphate-D-xylose 4-epimerase; UDP-D-xylose 4-epimerase
Systematic name: UDP-L-arabinose 4-epimerase
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, CAS registry number: 9024-18-4
References:
1.  Feingold, D.S., Neufeld, E.F. and Hassid, W.Z. The 4-epimerization and decarboxylation of uridine diphosphate D-glucuronic acid by extracts from Phaseolus aureus seedlings. J. Biol. Chem. 235 (1960) 910–913. [PMID: 13821949]
[EC 5.1.3.5 created 1965]
 
 
EC 5.1.3.6     
Accepted name: UDP-glucuronate 4-epimerase
Reaction: UDP-glucuronate = UDP-D-galacturonate
For diagram of the biosynthesis of UDP-L-arabinose, UDP-galacturonate and UDP-xylose, click here
Other name(s): uridine diphospho-D-galacturonic acid; UDP glucuronic epimerase; uridine diphosphoglucuronic epimerase; UDP-galacturonate 4-epimerase; uridine diphosphoglucuronate epimerase; UDP-D-galacturonic acid 4-epimerase
Systematic name: UDP-glucuronate 4-epimerase
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, CAS registry number: 9024-17-3
References:
1.  Feingold, D.S., Neufeld, E.F. and Hassid, W.Z. The 4-epimerization and decarboxylation of uridine diphosphate D-glucuronic acid by extracts from Phaseolus aureus seedlings. J. Biol. Chem. 235 (1960) 910–913. [PMID: 13821949]
[EC 5.1.3.6 created 1965]
 
 
EC 5.1.3.7     
Accepted name: UDP-N-acetylglucosamine 4-epimerase
Reaction: UDP-N-acetyl-α-D-glucosamine = UDP-N-acetyl-α-D-galactosamine
Other name(s): UDP acetylglucosamine epimerase; uridine diphosphoacetylglucosamine epimerase; uridine diphosphate N-acetylglucosamine-4-epimerase; uridine 5′-diphospho-N-acetylglucosamine-4-epimerase; UDP-N-acetyl-D-glucosamine 4-epimerase
Systematic name: UDP-N-acetyl-α-D-glucosamine 4-epimerase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9024-16-2
References:
1.  Glaser, L. The biosynthesis of N-acetylgalactosamine. J. Biol. Chem. 234 (1959) 2801–2805. [PMID: 13828347]
2.  Kornfeld, S. and Glaser, L. The synthesis of thymidine-linked sugars. V. Thymidine diphosphate-amino sugars. J. Biol. Chem. 237 (1962) 3052–3059. [PMID: 14034827]
[EC 5.1.3.7 created 1965]
 
 
EC 5.1.3.8     
Accepted name: N-acylglucosamine 2-epimerase
Reaction: N-acyl-D-glucosamine = N-acyl-D-mannosamine
Other name(s): acylglucosamine 2-epimerase; N-acetylglucosamine 2-epimerase
Systematic name: N-acyl-D-glucosamine 2-epimerase
Comments: Requires catalytic amounts of ATP.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 37318-34-6
References:
1.  Ghosh, S. and Roseman, S. The sialic acids. V. N-Acyl-D-glucosamine 2-epimerase. J. Biol. Chem. 240 (1965) 1531–1536. [PMID: 14285488]
[EC 5.1.3.8 created 1972]
 
 
EC 5.1.3.9     
Accepted name: N-acylglucosamine-6-phosphate 2-epimerase
Reaction: N-acyl-D-glucosamine 6-phosphate = N-acyl-D-mannosamine 6-phosphate
Other name(s): acylglucosamine-6-phosphate 2-epimerase; acylglucosamine phosphate 2-epimerase
Systematic name: N-acyl-D-glucosamine-6-phosphate 2-epimerase
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 37318-35-7
References:
1.  Ghosh, S. and Roseman, S. The sialic acids. IV. N-Acyl-D-glucosamine 6-phosphate 2-epimerase. J. Biol. Chem. 240 (1965) 1525–1530. [PMID: 14285487]
[EC 5.1.3.9 created 1972]
 
 
EC 5.1.3.10     
Accepted name: CDP-paratose 2-epimerase
Reaction: CDP-α-D-paratose = CDP-α-D-tyvelose
For diagram of CDP-abequose, CDP-ascarylose, CDP-paratose and CDP-tyrelose biosynthesis, click here
Glossary: CDP-α-D-tyvelose = CDP-3,6-dideoxy-α-D-mannose = CDP-3,6-dideoxy-α-D-arabino-hexose
CDP-α-D-paratose = CDP-3,6-dideoxy-α-D-glucose = CDP-3,6-dideoxy-α-D-ribo-hexose
Other name(s): CDP-paratose epimerase; cytidine diphosphoabequose epimerase; cytidine diphosphodideoxyglucose epimerase; cytidine diphosphoparatose epimerase; cytidine diphosphate paratose-2-epimerase; CDP-abequose epimerase (incorrect); CDP-D-abequose 2-epimerase (incorrect); CDP-tyvelose 2-epimerase,
Systematic name: CDP-3,6-dideoxy-D-glucose 2-epimerase
Comments: Requires NAD+.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 37318-36-8
References:
1.  Matsuhashi, S. Enzymatic synthesis of cytidine diphosphate 3,6-dideoxyhexoses. II. Reversible 2-epimerization of cytidine diphosphate paratose. J. Biol. Chem. 241 (1966) 4275–4282. [PMID: 5924649]
2.  Liu, H.-W. and Thorson, J.S. Pathways and mechanisms in the biogenesis of novel deoxysugars by bacteria. Annu. Rev. Microbiol. 48 (1994) 223–256. [PMID: 7826006]
3.  Koropatkin, N.M., Liu, H.W. and Holden, H.M. High resolution x-ray structure of tyvelose epimerase from Salmonella typhi. J. Biol. Chem. 278 (2003) 20874–20881. [PMID: 12642575]
[EC 5.1.3.10 created 1972, modified 2005]
 
 
EC 5.1.3.11     
Accepted name: cellobiose epimerase
Reaction: cellobiose = 4-O-β-D-glucopyranosyl-D-mannose
Glossary: cellobiose = 4-O-β-D-glucopyranosyl-D-glucose
Systematic name: cellobiose 2-epimerase
Comments: The enzyme catalyses the interconversion between D-glucose and D-mannose residues at the reducing end of β-1,4-linked disaccharides by epimerizing the hydroxyl group at the C-2 position of the glucose moiety.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37318-37-9
References:
1.  Tyler, T.R. and Leatherwood, J.M. Epimerization of disaccharides by enzyme preparations from Ruminococcus albus. Arch. Biochem. Biophys. 119 (1967) 363–367. [PMID: 6069974]
2.  Ito, S., Taguchi, H., Hamada, S., Kawauchi, S., Ito, H., Senoura, T., Watanabe, J., Nishimukai, M., Ito, S. and Matsui, H. Enzymatic properties of cellobiose 2-epimerase from Ruminococcus albus and the synthesis of rare oligosaccharides by the enzyme. Appl. Microbiol. Biotechnol. 79 (2008) 433–441. [PMID: 18392616]
3.  Fujiwara, T., Saburi, W., Inoue, S., Mori, H., Matsui, H., Tanaka, I. and Yao, M. Crystal structure of Ruminococcus albus cellobiose 2-epimerase: structural insights into epimerization of unmodified sugar. FEBS Lett. 587 (2013) 840–846. [PMID: 23462136]
[EC 5.1.3.11 created 1972]
 
 
EC 5.1.3.12     
Accepted name: UDP-glucuronate 5′-epimerase
Reaction: UDP-α-D-glucuronate = UDP-β-L-iduronate
For diagram of UDP-L-arabinose, UDP-galacturonate and UDP-xylose biosynthesis, click here
Other name(s): uridine diphosphoglucuronate 5′-epimerase; UDP-glucuronic acid 5′-epimerase; C-5-uronosyl epimerase
Systematic name: UDP-α-D-glucuronate 5′-epimerase
Comments: Requires NAD+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37318-38-0
References:
1.  Jacobson, B. and Davidson, E.A. Biosynthesis of uronic acids by skin enzymes. I. Uridine diphosphate-D-glucuronic acid-5-epimerase. J. Biol. Chem. 237 (1962) 638–642. [PMID: 14450717]
[EC 5.1.3.12 created 1972]
 
 
EC 5.1.3.13     
Accepted name: dTDP-4-dehydrorhamnose 3,5-epimerase
Reaction: dTDP-4-dehydro-6-deoxy-α-D-glucose = dTDP-4-dehydro-β-L-rhamnose
For diagram of dtdp-6-deoxyhexose biosynthesis, click here and for diagram of 6-deoxyhexose biosynthesis, click here
Glossary: dTDP-4-dehydro-β-L-rhamnose = dTDP-4-dehydro-6-deoxy-β-L-mannose
Other name(s): dTDP-L-rhamnose synthetase; dTDP-L-rhamnose synthase; thymidine diphospho-4-ketorhamnose 3,5-epimerase; TDP-4-ketorhamnose 3,5-epimerase; dTDP-4-dehydro-6-deoxy-D-glucose 3,5-epimerase; TDP-4-keto-L-rhamnose-3,5-epimerase
Systematic name: dTDP-4-dehydro-6-deoxy-α-D-glucose 3,5-epimerase
Comments: The enzyme occurs in a complex with EC 1.1.1.133 dTDP-4-dehydrorhamnose reductase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37318-39-1
References:
1.  Gaugler, R.W. and Gabriel, O. Biological mechanisms involved in the formation of deoxy sugars. VII. Biosynthesis of 6-deoxy-L-talose. J. Biol. Chem. 248 (1973) 6041–6049. [PMID: 4199258]
2.  Melo, A. and Glaser, L. The mechanism of 6-deoxyhexose synthesis. II. Conversion of deoxythymidine diphosphate 4-keto-6-deoxy-D-glucose to deoxythymidine diphosphate L-rhamnose. J. Biol. Chem. 243 (1968) 1475–1478. [PMID: 4384782]
[EC 5.1.3.13 created 1972]
 
 
EC 5.1.3.14     
Accepted name: UDP-N-acetylglucosamine 2-epimerase (non-hydrolysing)
Reaction: UDP-N-acetyl-α-D-glucosamine = UDP-N-acetyl-α-D-mannosamine
For diagram of UDP-N-acetylgalactosamine and UDP-N-acetylmannosamine biosynthesis, click here
Other name(s): UDP-N-acetylglucosamine 2′-epimerase (ambiguous); uridine diphosphoacetylglucosamine 2′-epimerase (ambiguous); uridine diphospho-N-acetylglucosamine 2′-epimerase (ambiguous); uridine diphosphate-N-acetylglucosamine-2′-epimerase (ambiguous); rffE (gene name); mnaA (gene name); UDP-N-acetyl-D-glucosamine 2-epimerase
Systematic name: UDP-N-acetyl-α-D-glucosamine 2-epimerase
Comments: This bacterial enzyme catalyses the reversible interconversion of UDP-GlcNAc and UDP-ManNAc. The latter is used in a variety of bacterial polysaccharide biosyntheses. cf. EC 3.2.1.183, UDP-N-acetylglucosamine 2-epimerase (hydrolysing).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9037-71-2
References:
1.  Kawamura, T., Kimura, M., Yamamori, S. and Ito, E. Enzymatic formation of uridine diphosphate N-acetyl-D-mannosamine. J. Biol. Chem. 253 (1978) 3595–3601. [PMID: 418068]
2.  Meier-Dieter, U., Starman, R., Barr, K., Mayer, H. and Rick, P.D. Biosynthesis of enterobacterial common antigen in Escherichia coli. Biochemical characterization of Tn10 insertion mutants defective in enterobacterial common antigen synthesis. J. Biol. Chem. 265 (1990) 13490–13497. [PMID: 2166030]
3.  Morgan, P. M., Sala, R. F., and Tanner, M. E. Eliminations in the reactions catalyzed by UDP-N-acetylglucosamine 2-epimerase. J. Am. Chem. Soc. 119 (1997) 10269–10277.
4.  Campbell, R.E., Mosimann, S.C., Tanner, M.E. and Strynadka, N.C. The structure of UDP-N-acetylglucosamine 2-epimerase reveals homology to phosphoglycosyl transferases. Biochemistry 39 (2000) 14993–15001. [PMID: 11106477]
5.  Samuel, J. and Tanner, M.E. Active site mutants of the "non-hydrolyzing" UDP-N-acetylglucosamine 2-epimerase from Escherichia coli. Biochim. Biophys. Acta 1700 (2004) 85–91. [PMID: 15210128]
6.  Soldo, B., Lazarevic, V., Pooley, H.M. and Karamata, D. Characterization of a Bacillus subtilis thermosensitive teichoic acid-deficient mutant: gene mnaA (yvyH) encodes the UDP-N-acetylglucosamine 2-epimerase. J. Bacteriol. 184 (2002) 4316–4320. [PMID: 12107153]
[EC 5.1.3.14 created 1976, modified 2012]
 
 
EC 5.1.3.15     
Accepted name: glucose-6-phosphate 1-epimerase
Reaction: α-D-glucose 6-phosphate = β-D-glucose 6-phosphate
Systematic name: D-glucose-6-phosphate 1-epimerase
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, CAS registry number: 37259-65-7
References:
1.  Wurster, B. and Hess, B. Glucose-6-phosphate-1-epimerase from baker's yeast. A new enzyme. FEBS Lett. 23 (1972) 341–348. [PMID: 11946648]
[EC 5.1.3.15 created 1976]
 
 
EC 5.1.3.16     
Accepted name: UDP-glucosamine 4-epimerase
Reaction: UDP-α-D-glucosamine = UDP-α-D-galactosamine
Systematic name: UDP-α-D-glucosamine 4-epimerase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Maley, F. and Maley, G.F. The enzymic conversion of glucosamine to galactosamine. Biochim. Biophys. Acta 31 (1959) 577–578. [PMID: 13628700]
2.  Silbert, J.E. and Brown, D.H. Enzymic synthesis of uridine diphosphate glucosamine and heparin from [14C]glucosamine by a mouse mast-cell tumor. Biochim. Biophys. Acta 54 (1961) 590–592. [PMID: 14039274]
[EC 5.1.3.16 created 1984]
 
 
EC 5.1.3.17     
Accepted name: heparosan-N-sulfate-glucuronate 5-epimerase
Reaction: Epimerization of D-glucuronate in heparosan-N-sulfate to L-iduronate.
Other name(s): heparosan epimerase; heparosan-N-sulfate-D-glucuronosyl 5-epimerase; C-5 uronosyl epimerase; polyglucuronate epimerase; D-glucuronyl C-5 epimerase; poly[(1,4)-β-D-glucuronosyl-(1,4)-N-sulfo-α-D-glucosaminyl] glucurono-5-epimerase
Systematic name: poly[(1→4)-β-D-glucuronosyl-(1→4)-N-sulfo-α-D-glucosaminyl] glucurono-5-epimerase
Comments: The enzyme acts on D-glucosyluronate residues in N-sulfated heparosan polymers, converting them to L-iduronate, thus modifying the polymer to heparan-N-sulfate. The enzyme requires that at least the N-acetylglucosamine residue linked to C-4 of the substrate has been deacetylated and N-sulfated, and activity is highest with fully N-sulfated substrate. It does not act on glucuronate residues that are O-sulfated or are adjacent to N-acetylglucosamine residues that are O-sulfated at the 6 position. Thus the epimerization from D-glucuronate to L-iduronate occurs after N-sulfation of glucosamine residues but before O-sulfation. Not identical with EC 5.1.3.19 chondroitin-glucuronate 5-epimerase or with EC 5.1.3.36, heparosan-glucuronate 5-epimerase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 112567-86-9
References:
1.  Jacobsson, I., Bäckström, G., Höök, M., Lindahl, U., Feingold, D.S., Malmström, A. and Rodén, L. Biosynthesis of heparin. Assay and properties of the microsomal uronosyl C-5 epimerase. J. Biol. Chem. 254 (1979) 2975–2982. [PMID: 107165]
2.  Jacobsson, I., Lindahl, U., Jensen, J.W., Roden, L., Prihar, H. and Feingold, D.S. Biosynthesis of heparin. Substrate specificity of heparosan N-sulfate D-glucuronosyl 5-epimerase. J. Biol. Chem. 259 (1984) 1056–1063. [PMID: 6420398]
3.  Hagner-McWhirter, A., Hannesson, H.H., Campbell, P., Westley, J., Roden, L., Lindahl, U. and Li, J.P. Biosynthesis of heparin/heparan sulfate: kinetic studies of the glucuronyl C5-epimerase with N-sulfated derivatives of the Escherichia coli K5 capsular polysaccharide as substrates. Glycobiology 10 (2000) 159–171. [PMID: 10642607]
[EC 5.1.3.17 created 1984, modified 2015]
 
 
EC 5.1.3.18     
Accepted name: GDP-mannose 3,5-epimerase
Reaction: GDP-α-D-mannose = GDP-β-L-galactose
Other name(s): GDP-D-mannose:GDP-L-galactose epimerase; guanosine 5′-diphosphate D-mannose:guanosine 5′-diphosphate L-galactose epimerase
Systematic name: GDP-α-D-mannose 3,5-epimerase
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 72162-82-4
References:
1.  Barber, G.A. and Hebda, P.A. GDP-D-mannose: GDP-L-galactose epimerase from Chlorella pyrenoidosa. Methods Enzymol. 83 (1982) 522–525. [PMID: 7098948]
2.  Hebda, P.A., Behrman, E.J. and Barber, G.A. The guanosine 5′-diphosphate D-mannose: guanosine 5′-diphosphate L-galactose epimerase of Chlorella pyrenoidosa. Chemical synthesis of guanosine 5′-diphosphate L-galactose and further studies of the enzyme and the reaction it catalyzes. Arch. Biochem. Biophys. 194 (1979) 496–502. [PMID: 443816]
[EC 5.1.3.18 created 1986]
 
 
EC 5.1.3.19     
Accepted name: chondroitin-glucuronate 5-epimerase
Reaction: chondroitin D-glucuronate = dermatan L-iduronate
For diagram of the later stages of chondroitin biosynthesis, click here
Other name(s): polyglucuronate 5-epimerase; dermatan-sulfate 5-epimerase; urunosyl C-5 epimerase; chondroitin D-glucuronosyl 5-epimerase
Systematic name: chondroitin-D-glucuronate 5-epimerase
Comments: Not identical with EC 5.1.3.17 heparosan-N-sulfate-glucuronate 5-epimerase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 70766-66-4
References:
1.  Malmström, A. and Åberg, L. Biosynthesis of dermatan sulphate. Assay and properties of the uronosyl C-5 epimerase. Biochem. J. 201 (1982) 489–493. [PMID: 7092807]
[EC 5.1.3.19 created 1986]
 
 
EC 5.1.3.20     
Accepted name: ADP-glyceromanno-heptose 6-epimerase
Reaction: ADP-D-glycero-D-manno-heptose = ADP-L-glycero-D-manno-heptose
Systematic name: ADP-L-glycero-D-manno-heptose 6-epimerase
Comments: Requires NAD+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 85030-75-7
References:
1.  Ding, L., Seto, B.L., Ahmed, S.A., Coleman, W.G., Jr. Purification and properties of the Escherichia coli K-12 NAD-dependent nucleotide diphosphosugar epimerase, ADP-L-glycero-D-manno-heptose 6-epimerase. J. Biol. Chem. 269 (1994) 24384–24390. [PMID: 7929099]
2.  Raetz, C.R.H. Biochemistry of endotoxins. Annu. Rev. Biochem. 58 (1990) 129–170. [PMID: 1695830]
[EC 5.1.3.20 created 1999]
 
 
EC 5.1.3.21     
Accepted name: maltose epimerase
Reaction: α-maltose = β-maltose
Systematic name: maltose 1-epimerase
Comments: The enzyme catalyses the interconversion of α and β anomers of maltose more effectively than those of disaccharides such as lactose and cellobiose.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 166799-98-0
References:
1.  Shirokane, Y. and Suzuki, M. A novel enzyme, maltose 1-epimerase from Lactobacillus brevis IFO 3345. FEBS Lett. 367 (1995) 177–179. [PMID: 7796915]
[EC 5.1.3.21 created 2002]
 
 


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