Accepted name: sulfoacetaldehyde reductase
Reaction: isethionate + NADP+ = 2-sulfoacetaldehyde + NADPH + H+
Glossary: isethionate = 2-hydroxyethanesulfonate
2-sulfoacetaldehyde = 2-oxoethanesulfonate
Other name(s): isfD (gene name)
Systematic name: isethionate:NADP+ oxidoreductase
Comments: Catalyses the reaction only in the opposite direction. Involved in taurine degradation. The bacterium Chromohalobacter salexigens strain DSM 3043 possesses two enzymes that catalyse this reaction, a constitutive enzyme (encoded by isfD2) and an inducible enzyme (encoded by isfD). The latter is induced by taurine, and is responsible for most of the activity observed in taurine-grown cells.
1.  Krejcik, Z., Hollemeyer, K., Smits, T.H. and Cook, A.M. Isethionate formation from taurine in Chromohalobacter salexigens: purification of sulfoacetaldehyde reductase. Microbiology 156 (2010) 1547–1555. [PMID: 20133363]
[EC created 2011]
Accepted name: sulfoacetaldehyde dehydrogenase
Reaction: 2-sulfoacetaldehyde + H2O + NAD+ = sulfoacetate + NADH + 2 H+
Glossary: 2-sulfoacetaldehyde = 2-oxoethanesulfonate
taurine = 2-aminoethanesulfonate
Other name(s): SafD
Systematic name: 2-sulfoacetaldehyde:NAD+ oxidoreductase
Comments: This reaction is part of a bacterial pathway that can utilize the amino group of taurine as a sole source of nitrogen for growth. At physiological concentrations, NAD+ cannot be replaced by NADP+. The enzyme is specific for sulfoacetaldehyde, as formaldehyde, acetaldehyde, betaine aldehyde, propanal, glyceraldehyde, phosphonoacetaldehyde, glyoxylate, glycolaldehyde and 2-oxobutyrate are not substrates.
1.  Krejčík, Z., Denger, K., Weinitschke, S., Hollemeyer, K., Pačes, V., Cook, A.M. and Smits, T.H.M. Sulfoacetate released during the assimilation of taurine-nitrogen by Neptuniibacter caesariensis: purification of sulfoacetaldehyde dehydrogenase. Arch. Microbiol. 190 (2008) 159–168. [PMID: 18506422]
[EC created 2008]
Accepted name: taurine dehydrogenase
Reaction: taurine + H2O + acceptor = 2-sulfoacetaldehyde + NH3 + reduced acceptor
Glossary: 2-sulfoacetaldehyde = 2-oxoethanesulfonate
taurine = 2-aminoethanesulfonate
Other name(s): taurine:(acceptor) oxidoreductase (deaminating)
Systematic name: taurine:acceptor oxidoreductase (deaminating)
1.  Kondo, H., Kagotani, K., Oshima, M. and Ishimoto, M. Purification and some properties of taurine dehydrogenase from a bacterium. J. Biochem. (Tokyo) 73 (1973) 1269–1278. [PMID: 4724302]
[EC created 1976]
Accepted name: tauropine dehydrogenase
Reaction: tauropine + NAD+ + H2O = taurine + pyruvate + NADH + H+
Glossary: tauropine = N2-(D-1-carboxyethyl)-2-aminoethanesulfonate
Other name(s): 2-N-(D-1-carboxyethyl)taurine:NAD+ oxidoreductase (taurine-forming)
Systematic name: N2-(D-1-carboxyethyl)taurine:NAD+ oxidoreductase (taurine-forming)
Comments: In the reverse reaction, alanine can act instead of taurine, but more slowly, and 2-oxobutanoate and 2-oxopentanoate can act instead of pyruvate.
1.  Gäde, G. Purification and properties of tauropine dehydrogenase from the shell adductor muscle of the ormer, Haliotis lamellosa. Eur. J. Biochem. 160 (1986) 311–318. [PMID: 3769931]
[EC created 1989]
Accepted name: hypotaurine dehydrogenase
Reaction: hypotaurine + H2O + NAD+ = taurine + NADH + H+
Systematic name: hypotaurine:NAD+ oxidoreductase
Comments: A molybdohemoprotein.
1.  Sumizu, K. Oxidation of hypotaurine in rat liver. Biochim. Biophys. Acta 63 (1962) 210–212. [PMID: 13979247]
[EC created 1972]
Accepted name: cysteamine dioxygenase
Reaction: cysteamine + O2 = hypotaurine
Glossary: cysteamine = 2-aminoethanethiol
Other name(s): ADO (gene name); persulfurase; cysteamine oxygenase; cysteamine:oxygen oxidoreductase
Systematic name: 2-aminoethanethiol:oxygen oxidoreductase
Comments: A non-heme iron protein that is involved in the biosynthesis of taurine. 3-Aminopropanethiol (homocysteamine) and 2-sulfanylethan-1-ol (2-mercaptoethanol) can also act as substrates, but glutathione, cysteine, and cysteine ethyl- and methyl esters are not good substrates [1,3].
1.  Cavallini, D., de Marco, C., Scandurra, R., Duprè, S. and Graziani, M.T. The enzymatic oxidation of cysteamine to hypotaurine. Purification and properties of the enzyme. J. Biol. Chem. 241 (1966) 3189–3196. [PMID: 5912113]
2.  Wood, J.L. and Cavallini, D. Enzymic oxidation of cysteamine to hypotaurine in the absence of a cofactor. Arch. Biochem. Biophys. 119 (1967) 368–372. [PMID: 6052430]
3.  Cavallini, D., Federici, G., Ricci, G., Duprè, S. and Antonucci, A. The specificity of cysteamine oxygenase. FEBS Lett. 56 (1975) 348–351. [PMID: 1157952]
4.  Richerson, R.B. and Ziegler, D.M. Cysteamine dioxygenase. Methods Enzymol. 143 (1987) 410–415. [PMID: 3657558]
5.  Dominy, J.E., Jr., Simmons, C.R., Hirschberger, L.L., Hwang, J., Coloso, R.M. and Stipanuk, M.H. Discovery and characterization of a second mammalian thiol dioxygenase, cysteamine dioxygenase. J. Biol. Chem. 282 (2007) 25189–25198. [PMID: 17581819]
[EC created 1972, modified 2006]
Accepted name: cysteine dioxygenase
Reaction: L-cysteine + O2 = 3-sulfinoalanine
Other name(s): cysteine oxidase
Systematic name: L-cysteine:oxygen oxidoreductase
Comments: Requires Fe2+ and NAD(P)H.
1.  Lombardini, J.B., Singer, T.P. and Boyer, P.D. Cystein oxygenase. II. Studies on the mechanism of the reaction with 18oxygen. J. Biol. Chem. 244 (1969) 1172–1175. [PMID: 5767301]
[EC created 1972, modified 1976]
Accepted name: taurine dioxygenase
Reaction: taurine + 2-oxoglutarate + O2 = sulfite + aminoacetaldehyde + succinate + CO2
Other name(s): 2-aminoethanesulfonate dioxygenase; α-ketoglutarate-dependent taurine dioxygenase
Systematic name: taurine, 2-oxoglutarate:oxygen oxidoreductase (sulfite-forming)
Comments: Requires FeII. The enzyme from Escherichia coli also acts on pentanesulfonate, 3-(N-morpholino)propanesulfonate and 2-(1,3-dioxoisoindolin-2-yl)ethanesulfonate, but at lower rates.
1.  Eichhorn, E., Van Der Poeg, J.R., Kertesz, M.A. and Leisinger, T. Characterization of α-ketoglutarate-dependent taurine dioxygenase from Escherichia coli. J. Biol. Chem. 272 (1997) 23031–23036. [PMID: 9287300]
[EC created 2000]
Transferred entry: taurochenodeoxycholate 6α-hydroxylase. Now EC, taurochenodeoxycholate 6α-hydroxylase
[EC created 2005, deleted 2018]
Accepted name: alkanesulfonate monooxygenase
Reaction: an alkanesulfonate + FMNH2 + O2 = an aldehyde + FMN + sulfite + H2O
Glossary: an alkanesulfonate = R-CH2-SO3-
an aldehyde = R-CHO
Other name(s): SsuD; sulfate starvation-induced protein 6; alkanesulfonate,reduced-FMN:oxygen oxidoreductase
Systematic name: alkanesulfonate,FMNH2:oxygen oxidoreductase
Comments: The enzyme from Escherichia coli catalyses the desulfonation of a wide range of aliphatic sulfonates (unsubstituted C1- to C14-sulfonates as well as substituted C2-sulfonates). Does not desulfonate taurine (2-aminoethanesulfonate) or aromatic sulfonates. Does not use FMN as a bound cofactor. Instead, it uses reduced FMN (i.e., FMNH2) as a substrate. FMNH2 is provided by SsuE, the associated FMN reductase (EC
1.  Eichhorn, E., van der Ploeg, J.R. and Leisinger, T. Characterization of a two-component alkanesulfonate monooxygenase from Escherichia coli. J. Biol. Chem. 274 (1999) 26639–26646. [PMID: 10480865]
[EC created 2002]
Accepted name: taurochenodeoxycholate 6α-hydroxylase
Reaction: (1) taurochenodeoxycholate + [reduced NADPH—hemoprotein reductase] + O2 = taurohyocholate + [oxidized NADPH—hemoprotein reductase] + H2O
(2) lithocholate + [reduced NADPH—hemoprotein reductase] + O2 = hyodeoxycholate + [oxidized NADPH—hemoprotein reductase] + H2O
Glossary: taurochenodeoxycholic acid = N-(3α,7α-dihydroxy-5β-cholan-24-oyl)taurine
taurohyocholic acid = N-(3α,6α,7α-trihydroxy-5β-cholan-24-oyl)taurine
hyodeoxycholate = 3α,6α-dihydroxy-5β-cholan-24-oate
lithocholate = 3α-hydroxy-5β-cholan-24-oate
Other name(s): CYP3A4; CYP4A21; taurochenodeoxycholate 6α-monooxygenase
Systematic name: taurochenodeoxycholate,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (6α-hydroxylating)
Comments: A cytochrome P-450 (heme-thiolate) protein. Requires cytochrome b5 for maximal activity. Acts on taurochenodeoxycholate, taurodeoxycholate and less readily on lithocholate and chenodeoxycholate. In adult pig (Sus scrofa), hyocholic acid replaces cholic acid as a primary bile acid [5].
1.  Araya, Z. and Wikvall, K. 6α-Hydroxylation of taurochenodeoxycholic acid and lithocholic acid by CYP3A4 in human liver microsomes. Biochim. Biophys. Acta 1438 (1999) 47–54. [PMID: 10216279]
2.  Araya, Z., Hellman, U. and Hansson, R. Characterisation of taurochenodeoxycholic acid 6α-hydroxylase from pig liver microsomes. Eur. J. Biochem. 231 (1995) 855–861. [PMID: 7649186]
3.  Kramer, W., Sauber, K., Baringhaus, K.H., Kurz, M., Stengelin, S., Lange, G., Corsiero, D., Girbig, F., Konig, W. and Weyland, C. Identification of the bile acid-binding site of the ileal lipid-binding protein by photoaffinity labeling, matrix-assisted laser desorption ionization-mass spectrometry, and NMR structure. J. Biol. Chem. 276 (2001) 7291–7301. [PMID: 11069906]
4.  Lundell, K., Hansson, R. and Wikvall, K. Cloning and expression of a pig liver taurochenodeoxycholic acid 6α-hydroxylase (CYP4A21): a novel member of the CYP4A subfamily. J. Biol. Chem. 276 (2001) 9606–9612. [PMID: 11113117]
5.  Lundell, K. and Wikvall, K. Gene structure of pig sterol 12α-hydroxylase (CYP8B1) and expression in fetal liver: comparison with expression of taurochenodeoxycholic acid 6α-hydroxylase (CYP4A21). Biochim. Biophys. Acta 1634 (2003) 86–96. [PMID: 14643796]
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 asEC, transferred 2018 to EC]
Accepted name: bile acid-CoA:amino acid N-acyltransferase
Reaction: choloyl-CoA + glycine = CoA + glycocholate
Glossary: choloyl-CoA = 3α,7α,12α-trihydroxy-5β-cholan-24-oyl-CoA
Other name(s): glycine—taurine N-acyltransferase; amino acid N-choloyltransferase; BAT; glycine N-choloyltransferase; BACAT; cholyl-CoA glycine-taurine N-acyltransferase; cholyl-CoA:taurine N-acyltransferase
Systematic name: choloyl-CoA:glycine N-choloyltransferase
Comments: Also acts on CoA derivatives of other bile acids. Taurine and 2-fluoro-β-alanine can act as substrates, but more slowly [4]. The enzyme can also conjugate fatty acids to glycine and can act as a very-long-chain acyl-CoA thioesterase [7]. Bile-acid—amino-acid conjugates serve as detergents in the gastrointestinal tract, solubilizing long chain fatty acids, mono- and diglycerides, fat-soluble vitamins and cholesterol [4]. This is the second enzyme in a two-step process leading to the conjugation of bile acids with amino acids; the first step is the conversion of bile acids into their acyl-CoA thioesters, which is catalysed by EC, cholate—CoA ligase.
1.  Czuba, B. and Vessey, D.A. Kinetic characterization of cholyl-CoA glycine-taurine N-acyltransferase from bovine liver. J. Biol. Chem. 255 (1980) 5296–5299. [PMID: 7372637]
2.  Jordan, T.W., Lee, R. and Lim, W.C. Isoelectric focussing of soluble and particulate benzoyl-CoA and cholyl-CoA:amino acid N-acyltransferases from rat liver. Biochem. Int. 1 (1980) 325–330.
3.  Vessey, D.A. The co-purification and common identity of cholyl CoA:glycine- and cholyl CoA:taurine-N-acyltransferase activities from bovine liver. J. Biol. Chem. 254 (1979) 2059–2063. [PMID: 422567]
4.  Johnson, M.R., Barnes, S., Kwakye, J.B. and Diasio, R.B. Purification and characterization of bile acid-CoA:amino acid N-acyltransferase from human liver. J. Biol. Chem. 266 (1991) 10227–10233. [PMID: 2037576]
5.  Falany, C.N., Xie, X., Wheeler, J.B., Wang, J., Smith, M., He, D. and Barnes, S. Molecular cloning and expression of rat liver bile acid CoA ligase. J. Lipid Res. 43 (2002) 2062–2071. [PMID: 12454267]
6.  He, D., Barnes, S. and Falany, C.N. Rat liver bile acid CoA:amino acid N-acyltransferase: expression, characterization, and peroxisomal localization. J. Lipid Res. 44 (2003) 2242–2249. [PMID: 12951368]
7.  O'Byrne, J., Hunt, M.C., Rai, D.K., Saeki, M. and Alexson, S.E. The human bile acid-CoA:amino acid N-acyltransferase functions in the conjugation of fatty acids to glycine. J. Biol. Chem. 278 (2003) 34237–34244. [PMID: 12810727]
[EC created 1983, modified 2005]
Accepted name: propanoyl-CoA C-acyltransferase
Reaction: 3α,7α,12α-trihydroxy-5β-cholanoyl-CoA + propanoyl-CoA = CoA + 3α,7α,12α-trihydroxy-24-oxo-5β-cholestanoyl-CoA
Other name(s): SCP2 (gene name); peroxisomal thiolase 2; sterol carrier protein-χ; SCPχ; PTE-2 (ambiguous); propionyl-CoA C2-trimethyltridecanoyltransferase; 3-oxopristanoyl-CoA hydrolase; 3-oxopristanoyl-CoA thiolase; peroxisome sterol carrier protein thiolase; sterol carrier protein; oxopristanoyl-CoA thiolase; peroxisomal 3-oxoacyl coenzyme A thiolase; SCPx; 4,8,12-trimethyltridecanoyl-CoA:propanoyl-CoA 2-C-4,8,12-trimethyltridecanoyltransferase
Systematic name: 3α,7α,12α-trihydroxy-5β-cholanoyl-CoA:propanoyl-CoA C-acyltransferase
Comments: Also acts on dihydroxy-5β-cholestanoyl-CoA and other branched chain acyl-CoA derivatives. The enzyme catalyses the penultimate step in the formation of bile acids. The bile acid moiety is transferred from the acyl-CoA thioester (RCO-SCoA) to either glycine or taurine (NH2R′) by EC, bile acid-CoA:amino acid N-acyltransferase [3].
1.  Pedersen, J.I. and Gustafsson, J. Conversion of 3α,7α,12α-trihydroxy-5β-cholestanoic acid into cholic acid by rat liver peroxisomes. FEBS Lett. 121 (1980) 345–348. [PMID: 7461136]
2.  Kase, F., Björkhem, I. and Pedersen, J.I. Formation of cholic acid from 3α,7α,12α-trihydroxy-5β-cholestanoic acid by rat liver peroxisomes. J. Lipid Res. 24 (1983) 1560–1567. [PMID: 6668450]
3.  Falany, C.N., Johnson, M.R., Barnes, S. and Diasio, R.B. Glycine and taurine conjugation of bile acids by a single enzyme. Molecular cloning and expression of human liver bile acid CoA:amino acid N-acyltransferase. J. Biol. Chem. 269 (1994) 19375–19379. [PMID: 8034703]
4.  Seedorf, U., Brysch, P., Engel, T., Schrage, K. and Assmann, G. Sterol carrier protein X is peroxisomal 3-oxoacyl coenzyme A thiolase with intrinsic sterol carrier and lipid transfer activity. J. Biol. Chem. 269 (1994) 21277–21283. [PMID: 8063752]
5.  Wanders, R.J.A., Denis, S., Wouters, F., Wirtz, K.W.A. and Seedorf, U. Sterol carrier protein X (SCPx) is a peroxisomal branched-chain β-ketothiolase specifically reacting with 3-oxo-pristanoyl-CoA: a new, unique role for SCPx in branched-chain fatty acid metabolism in peroxisomes. Biochem. Biophys. Res. Commun. 236 (1997) 565–569. [PMID: 9245689]
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 (EC created 2000, incorporated 2015)]
Accepted name: sulfoacetaldehyde acetyltransferase
Reaction: acetyl phosphate + sulfite = 2-sulfoacetaldehyde + phosphate
Glossary: 2-sulfoacetaldehyde = 2-oxoethanesulfonate
Other name(s): Xsc
Systematic name: acetyl-phosphate:sulfite S-acetyltransferase (acyl-phosphate hydrolysing, 2-oxoethyl-forming)
Comments: The reaction occurs in the reverse direction to that shown above. Requires Mg2+.
1.  Ruff, J., Denger, K. and Cook, A.M. Sulphoacetaldehyde acetyltransferase yields acetyl phosphate: purification from Alcaligenes defragrans and gene clusters in taurine degradation. Biochem. J. 369 (2003) 275–285. [PMID: 12358600]
[EC created 2003]
Accepted name: taurine—2-oxoglutarate transaminase
Reaction: taurine + 2-oxoglutarate = 2-sulfoacetaldehyde + L-glutamate
Glossary: 2-sulfoacetaldehyde = 2-oxoethanesulfonate
taurine = 2-aminoethanesulfonate
Other name(s): taurine aminotransferase; taurine transaminase; taurine—α-ketoglutarate aminotransferase; taurine—glutamate transaminase
Systematic name: taurine:2-oxoglutarate aminotransferase
Comments: A pyridoxal-phosphate protein. Also acts on D,L-3-amino-isobutanoate, β-alanine and 3-aminopropanesulfonate. Involved in the microbial utilization of β-alanine.
1.  Toyama, S., Misono, H. and Soda, K. Crystalline taurine:α-ketoglutarate aminotransferase from Achromobacter superficialis. Biochem. Biophys. Res. Commun. 46 (1972) 1374–1379. [PMID: 5012173]
2.  Cook, A.M. and Denger, K. Dissimilation of the C2 sulfonates. Arch. Microbiol. 179 (2002) 1–6. [PMID: 12471498]
[EC created 1976, modified 2003]
Accepted name: taurine—pyruvate aminotransferase
Reaction: taurine + pyruvate = L-alanine + 2-sulfoacetaldehyde
Glossary: taurine = 2-aminoethanesulfonate
hypotaurine = 2-aminoethanesulfinate
2-sulfoacetaldehyde = 2-oxoethanesulfonate
2-sulfinoacetaldehyde = 2-oxoethanesulfinate
Other name(s): Tpa
Systematic name: taurine:pyruvate aminotransferase
Comments: The enzyme from the bacterium Bilophila wadsworthia requires pyridoxal 5′-phosphate as a cofactor, and catalyses a reversible reaction that starts an anaerobic taurine degradation pathway. β-Alanine is also a significant amino group donor. The enzyme from the bacterium Pseudomonas denitrificans PD1222 can also use hypotaurine, producing 2-sulfinoacetaldehyde, which spontaneously hydrolyses to sulfite and acetaldehyde. Unlike, EC, taurine—2-oxoglutarate transaminase, 2-oxoglutarate cannot serve as an acceptor for the amino group.
1.  Laue, H. and Cook, A.M. Biochemical and molecular characterization of taurine:pyruvate transaminase from the anaerobe Bilophila wadsworthia. Eur. J. Biochem. 267 (2000) 6841–6848. [PMID: 11082195]
2.  Cook, A.M. and Denger, K. Dissimilation of the C2 sulfonates. Arch. Microbiol. 179 (2002) 1–6. [PMID: 12471498]
3.  Masepohl, B., Fuhrer, F. and Klipp, W. Genetic analysis of a Rhodobacter capsulatus gene region involved in utilization of taurine as a sulfur source. FEMS Microbiol. Lett. 205 (2001) 105–111. [PMID: 11728723]
4.  Felux, A.K., Denger, K., Weiss, M., Cook, A.M. and Schleheck, D. Paracoccus denitrificans PD1222 utilizes hypotaurine via transamination followed by spontaneous desulfination to yield acetaldehyde and, finally, acetate for growth. J. Bacteriol. 195 (2013) 2921–2930. [PMID: 23603744]
[EC created 2003]
Accepted name: choloylglycine hydrolase
Reaction: glycocholate + H2O = cholate + glycine
Glossary: glycocholate = N-(3α,7α,12α-trihydroxy-5β-cholan-24-oyl)glycine
cholate = 3α,7α,12α-trihydroxy-5β-cholan-24-oate
Other name(s): glycocholase; bile salt hydrolase; choloyltaurine hydrolase; 3α,7α,12α-trihydroxy-5β-cholan-24-oylglycine amidohydrolase
Systematic name: glycocholate amidohydrolase
Comments: Also acts on the 3α,12α-dihydroxy-derivative, and on choloyl-taurine.
1.  Nair, P.P., Gordon, M. and Reback, J. The enzymatic cleavage of the carbon-nitrogen bond in 3α,7α,12α-trihydroxy-5-β-cholan-24-oylglycine. J. Biol. Chem. 242 (1967) 7–11. [PMID: 6016335]
2.  Stellwag, E.J. and Hylemon, P.B. Purification and characterization of bile salt hydrolase from Bacteroides fragilis subsp. fragilis. Biochim. Biophys. Acta 452 (1976) 165–176. [PMID: 10993]
[EC created 1972]
Accepted name: chenodeoxycholoyltaurine hydrolase
Reaction: chenodeoxycholoyltaurine + H2O = chenodeoxycholate + taurine
Glossary: chenodeoxycholate = 3α,7α-dihydroxy-5β-cholan-24-oate
Systematic name: chenodeoxycholoyltaurine amidohydrolase
Comments: Some other taurine conjugates are hydrolysed, but not glycine conjugates of bile acids.
1.  Kawamoto, K., Horibe, I. and Uchida, K. Purification and characterization of a new hydrolase for conjugated bile acids, chenodeoxycholyltaurine hydrolase, from Bacteroides vulgatus. J. Biochem. (Tokyo) 106 (1989) 1049–1053. [PMID: 2628421]
[EC created 1992]
Transferred entry: taurine-transporting ATPase. Now EC, taurine-transporting ATPase
[EC created 2000, deleted 2018]
Accepted name: sulfinoalanine decarboxylase
Reaction: 3-sulfino-L-alanine = hypotaurine + CO2
Other name(s): cysteine-sulfinate decarboxylase; L-cysteinesulfinic acid decarboxylase; cysteine-sulfinate decarboxylase; CADCase/CSADCase; CSAD; cysteic decarboxylase; cysteinesulfinic acid decarboxylase; cysteinesulfinate decarboxylase; sulfoalanine decarboxylase; 3-sulfino-L-alanine carboxy-lyase
Systematic name: 3-sulfino-L-alanine carboxy-lyase (hypotaurine-forming)
Comments: A pyridoxal-phosphate protein. Also acts on L-cysteate. The 1992 edition of the Enzyme List erroneously gave the name sulfoalanine decarboxylase to this enzyme.
1.  Guion-Rain, M.C., Portemer, C. and Chatagner, F. Rat liver cysteine sulfinate decarboxylase: purification, new appraisal of the molecular weight and determination of catalytic properties. Biochim. Biophys. Acta 384 (1975) 265–276. [PMID: 236774]
2.  Jacobsen, J.G., Thomas, L.L. and Smith, L.H., Jr. Properties and distribution of mammalian L-cysteine sulfinate carboxy-lyases. Biochim. Biophys. Acta 85 (1964) 103–116. [PMID: 14159288]
[EC created 1961, deleted 1972, reinstated 1976, modified 1983, modified 1999]
Accepted name: cysteine lyase
Reaction: L-cysteine + sulfite = L-cysteate + hydrogen sulfide
Other name(s): cysteine (sulfite) lyase; L-cysteine hydrogen-sulfide-lyase (adding sulfite)
Systematic name: L-cysteine hydrogen-sulfide-lyase (adding sulfite; L-cysteate-forming)
Comments: A pyridoxal-phosphate protein. Can use a second molecule of cysteine (producing lanthionine), or other alkyl thiols, as a replacing agent.
1.  Tolosa, E.A., Chepurnova, N.K., Khomutov, R.M. and Severin, E.S. Reactions catalysed by cysteine lyase from the yolk sac of chicken embryo. Biochim. Biophys. Acta 171 (1969) 369–371. [PMID: 5813025]
[EC created 1972]
Accepted name: isethionate sulfite-lyase
Reaction: isethionate = acetaldehyde + sulfite
Glossary: isethionate = 2-hydroxyethanesulfonate
Other name(s): islA (gene name)
Systematic name: isethionate sulfite-lyase
Comments: The enzyme, characterized from the human gut bacterium Bilophila wadsworthia, participates in a taurine degradation pathway that leads to sulfide production. The active form of the enzyme contains a glycyl radical that is generated by a dedicated activating enzyme via chemistry involving S-adenosyl-L-methionine (SAM) and a [4Fe-4S] cluster.
1.  Peck, S.C., Denger, K., Burrichter, A., Irwin, S.M., Balskus, E.P. and Schleheck, D. A glycyl radical enzyme enables hydrogen sulfide production by the human intestinal bacterium Bilophila wadsworthia. Proc. Natl. Acad. Sci. USA 116 (2019) 3171–3176. [PMID: 30718429]
2.  Xing, M., Wei, Y., Zhou, Y., Zhang, J., Lin, L., Hu, Y., Hua, G.,, N. Nanjaraj Urs, A., Liu, D., Wang, F., Guo, C., Tong, Y., Li, M., Liu, Y., Ang, E.L., Zhao, H., Yuchi, Z. and Zhang, Y. Radical-mediated C-S bond cleavage in C2 sulfonate degradation by anaerobic bacteria. Nat. Commun. 10:1609 (2019). [PMID: 30962433]
[EC created 2021]
Accepted name: ABC-type taurine transporter
Reaction: ATP + H2O + taurine-[taurine-binding protein][side 1] = ADP + phosphate + taurine[side 2] + [taurine-binding protein][side 1]
Other name(s): tauABC (gene names); taurine ABC transporter; taurine-transporting ATPase
Systematic name: ATP phosphohydrolase (ABC-type, taurine-importing)
Comments: An ATP-binding cassette (ABC) type transporter, characterized by the presence of two similar ATP-binding domains/proteins and two integral membrane domains/proteins. Does not undergo phosphorylation during the transport process. A bacterial enzyme that interacts with an extracytoplasmic substrate binding protein and mediates the high affinity uptake of taurine. In Escherichia coli the enzyme imports a range of sulfonates (including taurine) that can be used as a source of sulfur.
1.  van der Ploeg, J.R., Weiss, M.A., Saller, E., Nashimoto, H., Saito, N., Kertesz, M.A. and Leisinger, T. Identification of sulfate starvation-regulated genes in Escherichia coli: a gene cluster involved in the utilization of taurine as a sulfur source. J. Bacteriol. 178 (1996) 5438–5446. [PMID: 8808933]
[EC created 2000 as EC, transferred 2018 to EC]