Accepted name: 3-dehydroquinate dehydratase
Reaction: 3-dehydroquinate = 3-dehydroshikimate + H2O
Glossary: quinate = (1R,3R,4R,5R)-1,3,4,5-tetrahydroxycyclohexanecarboxylic acid and is a cyclitol carboxylate
The numbering system used for the 3-dehydroquinate is that of the recommendations on cyclitols, sections I-8 and I-9: and is shown in the reaction diagram). The use of the term ’5-dehydroquinate’ for this compound is based on an earlier system of numbering.
Other name(s): 3-dehydroquinate hydrolase; DHQase; dehydroquinate dehydratase; 3-dehydroquinase; 5-dehydroquinase; dehydroquinase; 5-dehydroquinate dehydratase; 5-dehydroquinate hydro-lyase; 3-dehydroquinate hydro-lyase
Systematic name: 3-dehydroquinate hydro-lyase (3-dehydroshikimate-forming)
1.  Mitsuhashi, S. and Davis, B.D. Aromatic biosynthesis. XII. Conversion of 5-dehydroquinic acid to 5-dehydroshikimic acid by 5-dehydroquinase. Biochim. Biophys. Acta 15 (1954) 54–61. [PMID: 13198937]
2.  Mitsuhashi, S. and Davis, B.D. Aromatic biosynthesis. XIII. Conversion of quinic acid to 5-dehydroquinic acid by quinic dehydrogenase. Biochim. Biophys. Acta 15 (1954) 268–280. [PMID: 13208693]
[EC created 1961, modified 1976]
Accepted name: cyclohexa-1,5-dienecarbonyl-CoA hydratase
Reaction: 6-hydroxycyclohex-1-ene-1-carbonyl-CoA = cyclohexa-1,5-diene-1-carbonyl-CoA + H2O
Other name(s): cyclohexa-1,5-diene-1-carbonyl-CoA hydratase; dienoyl-CoA hydratase; cyclohexa-1,5-dienecarbonyl-CoA hydro-lyase (incorrect); 6-hydroxycyclohex-1-enecarbonyl-CoA hydro-lyase (cyclohexa-1,5-dienecarbonyl-CoA-forming)
Systematic name: 6-hydroxycyclohex-1-ene-1-carbonyl-CoA hydro-lyase (cyclohexa-1,5-diene-1-carbonyl-CoA-forming)
Comments: Forms part of the anaerobic benzoate degradation pathway, which also includes EC [glutaryl-CoA dehydrogenase (ETF)], EC (benzoyl-CoA reductase) and EC (3-hydroyxbutyryl-CoA dehydratase).
1.  Laempe, D., Eisenreich, W., Bacher, A. and Fuchs, G. Cyclohexa-1,5-diene-1-carboxyl-CoA hydratase, an enzyme involved in anaerobic metabolism of benzoyl-CoA in the denitrifying bacterium Thauera aromatica. Eur. J. Biochem. 255 (1998) 618–627. [PMID: 9738901]
2.  Harwood, C.S. and Gibson, J. Shedding light on anaerobic benzene ring degradation: a process unique to prokaryotes? J. Bacteriol. 179 (1997) 301–309. [PMID: 8990279]
3.  Koch, J., Eisenreich, W., Bacher, A. and Fuchs, G. Products of enzymatic reduction of benzoyl-CoA, a key reaction in anaerobic aromatic metabolism. Eur. J. Biochem. 211 (1993) 649–661. [PMID: 8436125]
[EC created 2000, modified 2001]
Accepted name: trans-feruloyl-CoA hydratase
Reaction: 4-hydroxy-3-methoxyphenyl-β-hydroxypropanoyl-CoA = feruloyl-CoA + H2O
Other name(s): trans-feruloyl-CoA hydro-lyase (incorrect); 4-hydroxy-3-methoxyphenyl-β-hydroxypropanoyl-CoA hydro-lyase (trans-feruloyl-CoA-forming)
Systematic name: 4-hydroxy-3-methoxyphenyl-β-hydroxypropanoyl-CoA hydro-lyase (feruloyl-CoA-forming)
1.  Narbad, A. and Gasson, M.J. Metabolism of ferulic acid via vanillin using a novel CoA-dependent pathway in a newly-isolated strain of Pseudomonas fluorescens. Microbiology 144 (1998) 1397–1405. [PMID: 9611814]
2.  Pometto, A.L. and Crawford, D.L. Whole-cell bioconversion of vanillin to vanillic acid by Streptomyces viridosporus. Appl. Environ. Microbiol. 45 (1983) 1582–1585. [PMID: 6870241]
[EC created 2000]
Transferred entry: cyclohexa-1,5-dienecarbonyl-CoA hydratase. Now EC, cyclohexa-1,5-dienecarbonyl-CoA hydratase
[EC created 2001, deleted 2001]
Accepted name: cyclohexyl-isocyanide hydratase
Reaction: N-cyclohexylformamide = cyclohexyl isocyanide + H2O
Other name(s): isonitrile hydratase; N-cyclohexylformamide hydro-lyase
Systematic name: N-cyclohexylformamide hydro-lyase (cyclohexyl-isocyanide-forming)
Comments: The enzyme from Pseudomonas putida strain N19-2 can also catalyse the hydration of other isonitriles to the corresponding N-substituted formamides. The enzyme has no metal requirements.
1.  Goda, M., Hashimoto, Y., Shimizu, S. and Kobayashi, M. Discovery of a novel enzyme, isonitrile hydratase, involved in nitrogen-carbon triple bond cleavage. J. Biol. Chem. 276 (2001) 23480–23485. [PMID: 11306561]
[EC created 2001]
Accepted name: cyanase
Reaction: cyanate + HCO3- + 2 H+ = NH3 + 2 CO2 (overall reaction)
(1a) cyanate + HCO3- + H+ = carbamate + CO2
(1b) carbamate + H+ = NH3 + CO2 (spontaneous)
Glossary: cyanate = NCO-
carbamate = H2N-CO-O-
Other name(s): cyanate lyase; cyanate hydrolase; cyanate aminohydrolase; cyanate C-N-lyase; cyanate hydratase
Systematic name: carbamate hydro-lyase
Comments: This enzyme, which is found in bacteria and plants, is used to decompose cyanate, which can be used as the sole source of nitrogen [6,7]. Reaction (1) can be considered as the reverse of ’carbamate = cyanate + H2O′, where this is assisted by reaction with bicarbonate and carbon dioxide (see mechanism above) [2], and hence is classified in sub-subclass 4.2.1. Bicarbonate functions as a recycling substrate [2].
1.  Anderson, P.M. Purification and properties of the inducible enzyme cyanase. Biochemistry 19 (1980) 2882–2888. [PMID: 6994799]
2.  Johnson, W.V. and Anderson, P.M. Bicarbonate is a recycling substrate for cyanase. J. Biol. Chem. 262 (1987) 9021–9025. [PMID: 3110153]
3.  Taussig, A. The synthesis of the induced enzyme, "cyanase", in E. coli. Biochim. Biophys. Acta 44 (1960) 510–519. [PMID: 13775509]
4.  Taussig, A. Some properties of the induced enzyme cyanase. Can. J. Biochem. 43 (1965) 1063–1069. [PMID: 5322950]
5.  Anderson, P.M., Korte, J.J. and Holcomb, T.A. Reaction of the N-terminal methionine residues in cyanase with diethylpyrocarbonate. Biochemistry 33 (1994) 14121–14125. [PMID: 7947823]
6.  Kozliak, E.I., Fuchs, J.A., Guilloton, M.B. and Anderson, P.M. Role of bicarbonate/CO2 in the inhibition of Escherichia coli growth by cyanate. J. Bacteriol. 177 (1995) 3213–3219. [PMID: 7768821]
7.  Walsh, M.A., Otwinowski, Z., Perrakis, A., Anderson, P.M. and Joachimiak, A. Structure of cyanase reveals that a novel dimeric and decameric arrangement of subunits is required for formation of the enzyme active site. Structure 8 (2000) 505–514. [PMID: 10801492]
[EC created 1972 as EC, transferred 1990 to EC, transferred 2001 to EC, modified 2007]
Accepted name: 2-hydroxyisoflavanone dehydratase
Reaction: (1) 2,4′,7-trihydroxyisoflavanone = daidzein + H2O
(2) 2,4′,5,7-tetrahydroxyisoflavanone = genistein + H2O
Glossary: daidzein = 4′,7-dihydroxyisoflavone
genistein = 4′,5,7-dihydroxyisoflavone
Other name(s): 2,7,4′-trihydroxyisoflavanone hydro-lyase; 2,7,4′-trihydroxyisoflavanone hydro-lyase (daidzein-forming)
Systematic name: 2,4′,7-trihydroxyisoflavanone hydro-lyase (daidzein-forming)
Comments: Catalyses the final step in the formation of the isoflavonoid skeleton. The reaction also occurs spontaneously.
1.  Hakamatsuka, T., Mori, K., Ishida, S., Ebizuka, Y and Sankawa, U. Purification of 2-hydroxyisoflavanone dehydratase from the cell cultures of Pueraria lobata. Phytochemistry 49 (1998) 497–505.
[EC created 2004, modified 2013]
Accepted name: bile-acid 7α-dehydratase
Reaction: 7α,12α-dihydroxy-3-oxochol-4-en-24-oyl-CoA = 12α-hydroxy-3-oxochola-4,6-dien-24-oyl-CoA + H2O
Other name(s): baiE (gene name); 7α,12α-dihydroxy-3-oxochol-4-enoate hydro-lyase; 7α,12α-dihydroxy-3-oxochol-4-enoate hydro-lyase (12α-hydroxy-3-oxochola-4,6-dienoate-forming); BA7 α dehydratase
Systematic name: 7α,12α-dihydroxy-3-oxochol-4-enoyl-CoA hydro-lyase (12α-hydroxy-3-oxochola-4,6-dienoyl-CoA-forming)
Comments: This enzyme, characterized from the gut bacterium Clostridium scindens (previously known as Eubacterium sp. strain VPI 12708), participates in the 7-dehydroxylation process associated with bile acid degradation.
1.  Mallonee, D.H., White, W.B. and Hylemon, P.B. Cloning and sequencing of a bile acid-inducible operon from Eubacterium sp. strain VPI 12708. J. Bacteriol. 172 (1990) 7011–7019. [PMID: 2254270]
2.  Dawson, J.A., Mallonee, D.H., Björkhem, I. and Hylemon, P.B. Expression and characterization of a C24 bile acid 7α-dehydratase from Eubacterium sp. strain VPI 12708 in Escherichia coli. J. Lipid Res. 37 (1996) 1258–1267. [PMID: 8808760]
3.  Bhowmik, S., Chiu, H.P., Jones, D.H., Chiu, H.J., Miller, M.D., Xu, Q., Farr, C.L., Ridlon, J.M., Wells, J.E., Elsliger, M.A., Wilson, I.A., Hylemon, P.B. and Lesley, S.A. Structure and functional characterization of a bile acid 7α dehydratase BaiE in secondary bile acid synthesis. Proteins 84 (2016) 316–331. [PMID: 26650892]
[EC created 2005, modified 2016]
Accepted name: 3α,7α,12α-trihydroxy-5β-cholest-24-enoyl-CoA hydratase
Reaction: (24R,25R)-3α,7α,12α,24-tetrahydroxy-5β-cholestanoyl-CoA = (24E)-3α,7α,12α-trihydroxy-5β-cholest-24-enoyl-CoA + H2O
Other name(s): 46 kDa hydratase 2; (24R,25R)-3α,7α,12α,24-tetrahydroxy-5β-cholestanoyl-CoA hydro-lyase
Systematic name: (24R,25R)-3α,7α,12α,24-tetrahydroxy-5β-cholestanoyl-CoA hydro-lyase [(24E)-3α,7α,12α-trihydroxy-5β-cholest-24-enoyl-CoA-forming]
Comments: This enzyme forms part of the rat peroxisomal multifunctional enzyme perMFE-2, which also exhibits a dehydrogenase activity. The enzyme is involved in the β-oxidation of the cholesterol side chain in the cholic-acid-biosynthesis pathway.
1.  Qin, Y.M., Haapalainen, A.M., Conry, D., Cuebas, D.A., Hiltunen, J.K. and Novikov, D.K. Recombinant 2-enoyl-CoA hydratase derived from rat peroxisomal multifunctional enzyme 2: role of the hydratase reaction in bile acid synthesis. Biochem. J. 328 (1997) 377–382. [PMID: 9371691]
2.  Xu, R. and Cuebas, D.A. The reactions catalyzed by the inducible bifunctional enzyme of rat liver peroxisomes cannot lead to the formation of bile acids. Biochem. Biophys. Res. Commun. 221 (1996) 271–278. [PMID: 8619845]
3.  Kinoshita, T., Miyata, M., Ismail, S.M., Fujimoto, Y., Kakinuma, K., Kokawa, N.I. and Morisaki, M. Synthesis and determination of stereochemistry of four diastereoisomers at the C-24 and C-25 positions of 3α,7α,12α,24-tetrahydroxy-5β-cholestan-26-oic acid and cholic acid. Chem. Pharm. Bull. 36 (1988) 134–141.
4.  Fujimoto, Y., Kinoshita, T., Oya, I., Kakinuma, K., Ismail, S.M., Sonoda, Y., Sato, Y. and Morisaki, M. Non-stereoselective conversion of the four diastereoisomers at the C-24 and C-25 positions of 3α,7α,12α,24-tetrahydroxy-5β-cholestan-26-oic acid and cholic acid. Chem. Pharm. Bull. 36 (1988) 142–145.
5.  Kurosawa, T., Sato, M., Nakano, H., Fujiwara, M., Murai, T., Yoshimura, T. and Hashimoto, T. Conjugation reactions catalyzed by bifunctional proteins related to β-oxidation in bile acid biosynthesis. Steroids 66 (2001) 107–114. [PMID: 11146090]
6.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [PMID: 12543708]
[EC created 2005]
Accepted name: ectoine synthase
Reaction: (2S)-4-acetamido-2-aminobutanoate = L-ectoine + H2O
Glossary: ectoine = (4S)-2-methyl-1,4,5,6-tetrahydropyrimidine-4-carboxylate
Other name(s): ectC (gene name); N-acetyldiaminobutyrate dehydratase; N-acetyldiaminobutanoate dehydratase; L-ectoine synthase; 4-N-acetyl-L-2,4-diaminobutanoate hydro-lyase (L-ectoine-forming); N4-acetyl-L-2,4-diaminobutanoate hydro-lyase (L-ectoine-forming)
Systematic name: (2S)-4-acetamido-2-aminobutanoate (L-ectoine-forming)
Comments: Ectoine is an osmoprotectant that is found in halophilic eubacteria. This enzyme is part of the ectoine biosynthesis pathway and only acts in the direction of ectoine formation. cf. EC, ectoine hydrolase.
1.  Peters, P., Galinski, E.A. and Truper, H.G. The biosynthesis of ectoine. FEMS Microbiol. Lett. 71 (1990) 157–162.
2.  Ono, H., Sawada, K., Khunajakr, N., Tao, T., Yamamoto, M., Hiramoto, M., Shinmyo, A., Takano, M. and Murooka, Y. Characterization of biosynthetic enzymes for ectoine as a compatible solute in a moderately halophilic eubacterium, Halomonas elongata. J. Bacteriol. 181 (1999) 91–99. [PMID: 9864317]
3.  Kuhlmann, A.U. and Bremer, E. Osmotically regulated synthesis of the compatible solute ectoine in Bacillus pasteurii and related Bacillus spp. Appl. Environ. Microbiol. 68 (2002) 772–783. [PMID: 11823218]
4.  Louis, P. and Galinski, E.A. Characterization of genes for the biosynthesis of the compatible solute ectoine from Marinococcus halophilus and osmoregulated expression in Escherichia coli. Microbiology 143 (1997) 1141–1149. [PMID: 9141677]
5.  Schwibbert, K., Marin-Sanguino, A., Bagyan, I., Heidrich, G., Lentzen, G., Seitz, H., Rampp, M., Schuster, S.C., Klenk, H.P., Pfeiffer, F., Oesterhelt, D. and Kunte, H.J. A blueprint of ectoine metabolism from the genome of the industrial producer Halomonas elongata DSM 2581 T. Environ. Microbiol. 13 (2011) 1973–1994. [PMID: 20849449]
[EC created 2006, modified 2017]
Accepted name: methylthioribulose 1-phosphate dehydratase
Reaction: 5-(methylsulfanyl)-D-ribulose 1-phosphate = 5-(methylsulfanyl)-2,3-dioxopentyl phosphate + H2O
Other name(s): 1-PMT-ribulose dehydratase; S-methyl-5-thio-D-ribulose-1-phosphate hydro-lyase; S-methyl-5-thio-D-ribulose-1-phosphate 4-hydro-lyase [5-(methylthio)-2,3-dioxopentyl-phosphate-forming]
Systematic name: 5-(methylsulfanyl)-D-ribulose-1-phosphate 4-hydro-lyase [5-(methylsulfanyl)-2,3-dioxopentyl-phosphate-forming]
Comments: This enzyme forms part of the methionine-salvage pathway.
1.  Furfine, E.S. and Abeles, R.H. Intermediates in the conversion of 5′-S-methylthioadenosine to methionine in Klebsiella pneumoniae. J. Biol. Chem. 263 (1988) 9598–9606. [PMID: 2838472]
2.  Wray, J.W. and Abeles, R.H. The methionine salvage pathway in Klebsiella pneumoniae and rat liver. Identification and characterization of two novel dioxygenases. J. Biol. Chem. 270 (1995) 3147–3153. [PMID: 7852397]
[EC created 2006]

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