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: 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: 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]