The Enzyme Database

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EC 1.1.1.52     
Accepted name: 3α-hydroxycholanate dehydrogenase (NAD+)
Reaction: lithocholate + NAD+ = 3-oxo-5β-cholan-24-oate + NADH + H+
For diagram of cholesterol catabolism (rings A, B and C), click here
Glossary: lithocholate = 3α-hydroxy-5β-cholan-24-oate
Other name(s): α-hydroxy-cholanate dehydrogenase; lithocholate:NAD+ oxidoreductase; 3α-hydroxycholanate dehydrogenase
Systematic name: lithocholate:NAD+ 3-oxidoreductase
Comments: Also acts on other 3α-hydroxysteroids with an acidic side-chain. cf. EC 1.1.1.392, 3α-hydroxycholanate dehydrogenase (NADP+).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9028-57-3
References:
1.  Hayaishi, O., Saito, Y., Jakoby, W.B. and Stohlman, E.F. Reversible enzymatic oxidation of bile acids. Arch. Biochem. Biophys. 56 (1955) 554–555. [DOI] [PMID: 14377608]
[EC 1.1.1.52 created 1961, modified 1976, modified 2016]
 
 
EC 1.1.1.159     
Accepted name: 7α-hydroxysteroid dehydrogenase
Reaction: cholate + NAD+ = 3α,12α-dihydroxy-7-oxo-5β-cholan-24-oate + NADH + H+
Glossary: cholate = 3α,7α,12α-trihydroxy-5β-cholan-24-oate
Other name(s): 7α-hydroxy steroid dehydrogenase; 7α-HSDH
Systematic name: 7α-hydroxysteroid:NAD+ 7-oxidoreductase
Comments: Catalyses the oxidation of the 7α-hydroxy group of bile acids and alcohols both in their free and conjugated forms. The Bacteroides fragilis and Clostridium enzymes can also utilize NADP+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 39361-64-3
References:
1.  Haslewood, E.S. and Haslewood, G.A.D. The specificity of a 7α-hydroxy steroid dehydrogenase from Escherichia coli. Biochem. J. 157 (1976) 207–210. [PMID: 786279]
2.  Macdonald, I.A. and Roach, P.D. Bile induction of 7α- and 7β-hydroxysteroid dehydrogenases in Clostridium absonum. Biochim. Biophys. Acta 665 (1981) 262–269. [DOI] [PMID: 6945134]
3.  Macdonald, I.A., Williams, C.N. and Mahony, D.E. 7α-Hydroxysteroid dehydrogenase from Escherichia coli B: preliminary studies. Biochim. Biophys. Acta 309 (1973) 243–253. [DOI] [PMID: 4581498]
4.  Macdonald, I.A., Williams, C.N., Mahony, D.E. and Christie, W.M. NAD- and NADP-dependent 7α-hydroxysteroid dehydrogenases from Bacteroides fragilis. Biochim. Biophys. Acta 384 (1975) 12–24. [DOI] [PMID: 236764]
[EC 1.1.1.159 created 1976, modified 1980]
 
 
EC 1.1.1.176     
Accepted name: 12α-hydroxysteroid dehydrogenase
Reaction: cholate + NADP+ = 3α,7α-dihydroxy-12-oxo-5β-cholan-24-oate + NADPH + H+
Glossary: cholate = 3α,7α,12α-trihydroxy-5β-cholan-24-oate
Other name(s): 12α-hydroxy steroid dehydrogenase; NAD+-dependent 12α-hydroxysteroid dehydrogenase; NADP+-12α-hydroxysteroid dehydrogenase
Systematic name: 12α-hydroxysteroid:NADP+ 12-oxidoreductase
Comments: Catalyses the oxidation of the 12α-hydroxy group of bile acids, both in their free and conjugated form. Also acts on bile alcohols.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 61642-40-8
References:
1.  Macdonald, I.A., Mahony, D.E., Jellett, J.F. and Meier, C.E. NAD-dependent 3α- and 12α-hydroxysteroid dehydrogenase activities from Eubacterium lentum ATCC no. 25559. Biochim. Biophys. Acta 489 (1977) 466–476. [DOI] [PMID: 201289]
2.  Mahony, D.E., Meier, C.E., Macdonald, I.A. and Holdeman, L.V. Bile salt degradation by nonfermentative clostridia. Appl. Environ. Microbiol. 34 (1977) 419–423. [PMID: 921266]
[EC 1.1.1.176 created 1978]
 
 
EC 1.1.1.201     
Accepted name: 7β-hydroxysteroid dehydrogenase (NADP+)
Reaction: a 7β-hydroxysteroid + NADP+ = a 7-oxosteroid + NADPH + H+
Other name(s): NADP-dependent 7β-hydroxysteroid dehydrogenase; 7β-hydroxysteroid dehydrogenase (NADP)
Systematic name: 7β-hydroxysteroid:NADP+ 7-oxidoreductase
Comments: Catalyses the oxidation of the 7β-hydroxy group of bile acids such as ursodeoxycholate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 79393-83-2
References:
1.  Hirano, S. and Masuda, N. Characterization of NADP-dependent 7β-hydroxysteroid dehydrogenases from Peptostreptococcus productus and Eubacterium aerofaciens. Appl. Environ. Microbiol. 43 (1982) 1057–1063. [PMID: 6954878]
2.  Macdonald, I.A. and Roach, P.D. Bile induction of 7α- and 7β-hydroxysteroid dehydrogenases in Clostridium absonum. Biochim. Biophys. Acta 665 (1981) 262–269. [DOI] [PMID: 6945134]
3.  Macdonald, I.A., Rochon, Y.P., Hutchison, D.M. and Holdeman, L.V. Formation of ursodeoxycholic acid from chenodeoxycholic acid by a 7β-hydroxysteroid dehydrogenase-elaborating Eubacterium aerofaciens strain cocultured with 7α-hydroxysteroid dehydrogenase-elaborating organisms. Appl. Environ. Microbiol. 44 (1982) 1187–1195. [PMID: 6758698]
[EC 1.1.1.201 created 1984]
 
 
EC 1.1.1.391     
Accepted name: 3β-hydroxycholanate 3-dehydrogenase (NAD+)
Reaction: isolithocholate + NAD+ = 3-oxo-5β-cholan-24-oate + NADH + H+
Glossary: isolithocholate = 3β-hydroxy-5β-cholan-24-oate
Other name(s): 3β-hydroxysteroid dehydrogenase
Systematic name: isolithocholate:NAD+ 3-oxidoreductase
Comments: This bacterial enzyme is involved, along with EC 1.1.1.52, 3α-hydroxycholanate dehydrogenase (NAD+), or EC 1.1.1.392, 3α-hydroxycholanate dehydrogenase (NADP+), in the modification of secondary bile acids to form 3β-bile acids (also known as iso-bile acids). The enzyme catalyses the reaction in the reduction direction in vivo. Also acts on related 3-oxo bile acids. cf. EC 1.1.1.393, 3β-hydroxycholanate 3-dehydrogenase (NADP+).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Edenharder, R., Pfutzner, A. and Hammann, R. Characterization of NAD-dependent 3 α- and 3 β-hydroxysteroid dehydrogenase and of NADP-dependent 7 β-hydroxysteroid dehydrogenase from Peptostreptococcus productus. Biochim. Biophys. Acta 1004 (1989) 230–238. [DOI] [PMID: 2752021]
2.  Edenharder, R. and Pfutzner, M. Partial purification and characterization of an NAD-dependent 3 β-hydroxysteroid dehydrogenase from Clostridium innocuum. Appl. Environ. Microbiol. 55 (1989) 1656–1659. [PMID: 2764572]
3.  Devlin, A.S. and Fischbach, M.A. A biosynthetic pathway for a prominent class of microbiota-derived bile acids. Nat. Chem. Biol. 11 (2015) 685–690. [DOI] [PMID: 26192599]
[EC 1.1.1.391 created 2016]
 
 
EC 1.1.1.392     
Accepted name: 3α-hydroxycholanate dehydrogenase (NADP+)
Reaction: lithocholate + NADP+ = 3-oxo-5β-cholan-24-oate + NADPH + H+
Glossary: lithocholate = 3α-hydroxy-5β-cholan-24-oate
Other name(s): α-hydroxy-cholanate dehydrogenase (ambiguous)
Systematic name: lithocholate:NADP+ 3-oxidoreductase
Comments: This bacterial enzyme is involved in the modification of secondary bile acids to form 3β-bile acids (also known as iso-bile acids) via a 3-oxo intermediate. The enzyme catalyses a reversible reaction in vitro. Also acts on related bile acids. cf. EC 1.1.1.52, 3α-hydroxycholanate dehydrogenase (NAD+).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9028-57-3
References:
1.  Devlin, A.S. and Fischbach, M.A. A biosynthetic pathway for a prominent class of microbiota-derived bile acids. Nat. Chem. Biol. 11 (2015) 685–690. [DOI] [PMID: 26192599]
[EC 1.1.1.392 created 2016]
 
 
EC 1.1.1.393     
Accepted name: 3β-hydroxycholanate 3-dehydrogenase (NADP+)
Reaction: isolithocholate + NADP+ = 3-oxo-5β-cholan-24-oate + NADPH + H+
Glossary: isolithocholate = 3β-hydroxy-5β-cholan-24-oate
Other name(s): 3β-hydroxysteroid dehydrogenase (ambiguous)
Systematic name: isolithocholate:NADP+ 3-oxidoreductase
Comments: This bacterial enzyme is involved, along with EC 1.1.1.52, 3α-hydroxycholanate dehydrogenase (NAD+), or EC 1.1.1.392, 3α-hydroxycholanate dehydrogenase (NADP+), in the modification of secondary bile acids to form 3β-bile acids (also known as iso-bile acids). The enzyme catalyses the reaction in the reduction direction in vivo. Also acts on related 3-oxo bile acids. cf. EC 1.1.1.391, 3β-hydroxycholanate 3-dehydrogenase (NAD+).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Akao, T., Akao, T., Hattori, M., Namba, T. and Kobashi, K. 3 β-Hydroxysteroid dehydrogenase of Ruminococcus sp. from human intestinal bacteria. J. Biochem. 99 (1986) 1425–1431. [PMID: 3458705]
2.  Devlin, A.S. and Fischbach, M.A. A biosynthetic pathway for a prominent class of microbiota-derived bile acids. Nat. Chem. Biol. 11 (2015) 685–690. [DOI] [PMID: 26192599]
[EC 1.1.1.393 created 2016]
 
 
EC 1.14.13.94      
Transferred entry: lithocholate 6β-hydroxylase. Now EC 1.14.14.138, lithocholate 6β-hydroxylase
[EC 1.14.13.94 created 2005, deleted 2018]
 
 
EC 1.14.13.97      
Transferred entry: taurochenodeoxycholate 6α-hydroxylase. Now EC 1.14.14.57, taurochenodeoxycholate 6α-hydroxylase
[EC 1.14.13.97 created 2005, deleted 2018]
 
 
EC 1.14.13.157      
Transferred entry: 1,8-cineole 2-exo-monooxygenase. Now EC 1.14.14.56, 1,8-cineole 2-exo-monooxygenase
[EC 1.14.13.157 created 2012, deleted 2017]
 
 
EC 1.14.14.56     
Accepted name: 1,8-cineole 2-exo-monooxygenase
Reaction: 1,8-cineole + [reduced NADPH—hemoprotein reductase] + O2 = 2-exo-hydroxy-1,8-cineole + [oxidized NADPH—hemoprotein reductase] + H2O
For diagram of 1,8-cineole catabolism, click here
Glossary: 1,8-cineole = 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane
2-exo-hydroxy-1,8-cineole = (1R,4S,6S)-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-6-ol
Other name(s): CYP3A4
Systematic name: 1,8-cineole,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (2-exo-hydroxylating)
Comments: A cytochrome P-450 (heme-thiolate) protein. The mammalian enzyme, expressed in liver microsomes, performs a variety of oxidation reactions of structurally unrelated compounds, including steroids, fatty acids, and xenobiotics. cf. EC 1.14.14.55, quinine 3-monooxygenase, EC 1.14.14.57, taurochenodeoxycholate 6-hydroxylase and EC 1.14.14.73, albendazole monooxygenase (sulfoxide-forming).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Miyazawa, M., Shindo, M. and Shimada, T. Oxidation of 1,8-cineole, the monoterpene cyclic ether originated from Eucalyptus polybractea, by cytochrome P450 3A enzymes in rat and human liver microsomes. Drug Metab. Dispos. 29 (2001) 200–205. [PMID: 11159812]
2.  Miyazawa, M. and Shindo, M. Biotransformation of 1,8-cineole by human liver microsomes. Nat. Prod. Lett. 15 (2001) 49–53. [DOI] [PMID: 11547423]
3.  Miyazawa, M., Shindo, M. and Shimada, T. Roles of cytochrome P450 3A enzymes in the 2-hydroxylation of 1,4-cineole, a monoterpene cyclic ether, by rat and human liver microsomes. Xenobiotica 31 (2001) 713–723. [DOI] [PMID: 11695850]
[EC 1.14.14.56 created 2012 as EC 1.14.13.157, transferred 2017 to EC 1.14.14.56, modified 2018]
 
 
EC 1.14.14.57     
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
For diagram of the biosynthesis of cholic-acid conjugates, click here
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].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 105669-85-0
References:
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. [DOI] [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. [DOI] [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. [DOI] [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. [DOI] [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. [DOI] [PMID: 14643796]
6.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [DOI] [PMID: 12543708]
[EC 1.14.14.57 created 2005 asEC 1.14.13.97, transferred 2018 to EC 1.14.14.57]
 
 
EC 1.14.14.138     
Accepted name: lithocholate 6β-hydroxylase
Reaction: lithocholate + [reduced NADPH—hemoprotein reductase] + O2 = 6β-hydroxylithocholate + [oxidized NADPH—hemoprotein reductase] + H2O
For diagram of the reaction of deoxycholate and related bile acids, click here
Glossary: lithocholate = 3α-hydroxy-5β-cholan-24-oate
6β-hydroxylithocholate = murideoxycholate = 3α,6β-dihydroxy-5β-cholan-24-oate
Other name(s): lithocholate 6β-monooxygenase; CYP3A10; 6β-hydroxylase; cytochrome P450 3A10; lithocholic acid 6β-hydroxylase
Systematic name: lithocholate,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (6β-hydroxylating)
Comments: A cytochrome P-450 (heme-thiolate) protein from Mesocricetus auratus (golden hamster). Expression of the gene for this enzyme is 50-fold higher in male compared to female hamsters [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9075-83-6
References:
1.  Teixeira, J. and Gil, G. Cloning, expression, and regulation of lithocholic acid 6β-hydroxylase. J. Biol. Chem. 266 (1991) 21030–21036. [PMID: 1840595]
2.  Chang, T.K., Teixeira, J., Gil, G. and Waxman, D.J. The lithocholic acid 6beta-hydroxylase cytochrome P-450, CYP 3A10, is an active catalyst of steroid-hormone 6β-hydroxylation. Biochem. J. 291 (1993) 429–433. [PMID: 8484723]
3.  Subramanian, A., Wang, J. and Gil, G. STAT 5 and NF-Y are involved in expression and growth hormone-mediated sexually dimorphic regulation of cytochrome P450 3A10/lithocholic acid 6β-hydroxylase. Nucleic Acids Res. 26 (1998) 2173–2178. [DOI] [PMID: 9547277]
4.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [DOI] [PMID: 12543708]
[EC 1.14.14.138 created 2005 as EC 1.14.13.94, transferred 2018 to EC 1.14.14.138]
 
 
EC 1.14.14.139     
Accepted name: 5β-cholestane-3α,7α-diol 12α-hydroxylase
Reaction: (1) 5β-cholestane-3α,7α-diol + [reduced NADPH—hemoprotein reductase] + O2 = 5β-cholestane-3α,7α,12α-triol + [oxidized NADPH—hemoprotein reductase] + H2O
(2) 7α-hydroxycholest-4-en-3-one + [reduced NADPH—hemoprotein reductase] + O2 = 7α,12α-dihydroxycholest-4-en-3-one + [oxidized NADPH—hemoprotein reductase] + H2O
(3) chenodeoxycholate + [reduced NADPH—hemoprotein reductase] + O2 = cholate + [oxidized NADPH—hemoprotein reductase] + H2O
For diagram of cholesterol catabolism (rings A, B and C), click here
Glossary: chenodeoxycholate = 3α,7α-dihydroxy-5β-cholan-24-oate
cholate = 3α,7α-12α-trihydroxy-5β-cholan-24-oate
Other name(s): 5β-cholestane-3α,7α-diol 12α-monooxygenase; sterol 12α-hydroxylase (ambiguous); CYP8B1; cytochrome P450 8B1; 7α-hydroxycholest-4-en-3-one 12α-hydroxylase; 7α-hydroxy-4-cholesten-3-one 12α-monooxygenase; chenodeoxycholate 12α monooxygenase
Systematic name: 5β-cholestane-3α,7α-diol,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (12α-hydroxylating)
Comments: A cytochrome P-450 (heme-thiolate) protein found in mammals. This is the key enzyme in the biosynthesis of the bile acid cholate. The enzyme can also hydroxylate 5β-cholestane-3α,7α-diol at the 25 and 26 position, but to a lesser extent [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Hansson, R. and Wikvall, K. Hydroxylations in biosynthesis and metabolism of bile acids. Catalytic properties of different forms of cytochrome P-450. J. Biol. Chem. 255 (1980) 1643–1649. [PMID: 6766451]
2.  Hansson, R. and Wikvall, K. Hydroxylations in biosynthesis of bile acids. Cytochrome P-450 LM4 and 12α-hydroxylation of 5β-cholestane-3α,7α-diol. Eur. J. Biochem. 125 (1982) 423–429. [DOI] [PMID: 6811268]
3.  Ishida, H., Noshiro, M., Okuda, K. and Coon, M.J. Purification and characterization of 7α-hydroxy-4-cholesten-3-one 12α-hydroxylase. J. Biol. Chem. 267 (1992) 21319–21323. [PMID: 1400444]
4.  Eggertsen, G., Olin, M., Andersson, U., Ishida, H., Kubota, S., Hellman, U., Okuda, K.I. and Björkhem, I. Molecular cloning and expression of rabbit sterol 12α-hydroxylase. J. Biol. Chem. 271 (1996) 32269–32275. [DOI] [PMID: 8943286]
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. [DOI] [PMID: 14643796]
6.  del Castillo-Olivares, A. and Gil, G. α1-Fetoprotein transcription factor is required for the expression of sterol 12α -hydroxylase, the specific enzyme for cholic acid synthesis. Potential role in the bile acid-mediated regulation of gene transcription. J. Biol. Chem. 275 (2000) 17793–17799. [DOI] [PMID: 10747975]
7.  Yang, Y., Zhang, M., Eggertsen, G. and Chiang, J.Y. On the mechanism of bile acid inhibition of rat sterol 12α-hydroxylase gene (CYP8B1) transcription: roles of α-fetoprotein transcription factor and hepatocyte nuclear factor 4alpha. Biochim. Biophys. Acta 1583 (2002) 63–73. [DOI] [PMID: 12069850]
8.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [DOI] [PMID: 12543708]
9.  Fan, L., Joseph, J.F., Durairaj, P., Parr, M.K. and Bureik, M. Conversion of chenodeoxycholic acid to cholic acid by human CYP8B1. Biol. Chem. 400 (2019) 625–628. [DOI] [PMID: 30465713]
[EC 1.14.14.139 created 2005 as EC 1.14.13.96, transferred 2018 to EC 1.14.14.139 (EC 1.14.18.8 created 2005 as EC 1.14.13.95, transferred 2015 to EC 1.14.18.8, incorporated 2020) , modified 2020]
 
 
EC 1.16.1.9     
Accepted name: ferric-chelate reductase (NADPH)
Reaction: 2 Fe(II)-siderophore + NADP+ + H+ = 2 Fe(III)-siderophore + NADPH
Other name(s): ferric chelate reductase (ambiguous); iron chelate reductase (ambiguous); NADPH:Fe3+-EDTA reductase; NADPH-dependent ferric reductase; yqjH (gene name); Fe(II):NADP+ oxidoreductase
Systematic name: Fe(II)-siderophore:NADP+ oxidoreductase
Comments: Contains FAD. The enzyme, which is widespread among bacteria, catalyses the reduction of ferric iron bound to a variety of iron chelators (siderophores), including ferric triscatecholates and ferric dicitrate, resulting in the release of ferrous iron. The enzyme from the bacterium Escherichia coli has the highest efficiency with the hydrolysed ferric enterobactin complex ferric N-(2,3-dihydroxybenzoyl)-L-serine [3]. cf. EC 1.16.1.7, ferric-chelate reductase (NADH) and EC 1.16.1.10, ferric-chelate reductase [NAD(P)H].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 120720-17-4
References:
1.  Bamford, V.A., Armour, M., Mitchell, S.A., Cartron, M., Andrews, S.C. and Watson, K.A. Preliminary X-ray diffraction analysis of YqjH from Escherichia coli: a putative cytoplasmic ferri-siderophore reductase. Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 64 (2008) 792–796. [DOI] [PMID: 18765906]
2.  Wang, S., Wu, Y. and Outten, F.W. Fur and the novel regulator YqjI control transcription of the ferric reductase gene yqjH in Escherichia coli. J. Bacteriol. 193 (2011) 563–574. [DOI] [PMID: 21097627]
3.  Miethke, M., Hou, J. and Marahiel, M.A. The siderophore-interacting protein YqjH acts as a ferric reductase in different iron assimilation pathways of Escherichia coli. Biochemistry 50 (2011) 10951–10964. [DOI] [PMID: 22098718]
[EC 1.16.1.9 created 1992 as EC 1.6.99.13, transferred 2002 to EC 1.16.1.7, transferred 2011 to EC 1.16.1.9, modified 2012, modified 2014]
 
 
EC 1.17.1.6      
Transferred entry: bile-acid 7α-dehydroxylase. Now EC 1.17.99.5, bile-acid 7α-dehydroxylase. It is now known that FAD is the acceptor and not NAD+ as was thought previously
[EC 1.17.1.6 created 2005, deleted 2006]
 
 
EC 1.17.98.1      
Deleted entry: bile-acid 7α-dehydroxylase. Now known to be catalyzed by multiple enzymes.
[EC 1.17.98.1 created 2005 as EC 1.17.1.6, transferred 2006 to EC 1.17.99.5, transferred 2014 to EC 1.17.98.1, deleted 2016]
 
 
EC 1.17.99.5      
Transferred entry: bile-acid 7α-dehydroxylase. Now classified as EC 1.17.98.1, bile-acid 7α-dehydroxylase.
[EC 1.17.99.5 created 2005 as EC 1.17.1.6, transferred 2006 to EC 1.17.99.5, deleted 2014]
 
 
EC 2.3.1.65     
Accepted name: bile acid-CoA:amino acid N-acyltransferase
Reaction: choloyl-CoA + glycine = CoA + glycocholate
For diagram of the biosynthesis of cholic-acid conjugates, click here
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 6.2.1.7, cholate—CoA ligase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 65979-40-0
References:
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. [DOI] [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. [DOI] [PMID: 12810727]
[EC 2.3.1.65 created 1983, modified 2005]
 
 
EC 2.8.2.14     
Accepted name: bile-salt sulfotransferase
Reaction: (1) 3′-phosphoadenylyl sulfate + glycolithocholate = adenosine 3′,5′-bisphosphate + glycolithocholate 3-sulfate
(2) 3′-phosphoadenylyl sulfate + taurolithocholate = adenosine 3′,5′-bisphosphate + taurolithocholate sulfate
For diagram of reaction, click here and for diagram of cholic acid conjugates biosynthesis, click here
Glossary: glycolithocholate 3-sulfate = N-(3α-sulfooxy-5β-cholan-24-oyl)glycine
Other name(s): BAST I; bile acid:3′-phosphoadenosine-5′-phosphosulfate sulfotransferase; bile salt:3′phosphoadenosine-5′-phosphosulfate:sulfotransferase; bile acid sulfotransferase I; glycolithocholate sulfotransferase; 3′-phosphoadenylyl-sulfate:glycolithocholate sulfotransferase
Systematic name: 3′-phosphoadenylyl-sulfate:glycolithocholate sulfonotransferase
Comments: The formation of sulfate esters of bile acids is an essential step in the prevention of toxicity by monohydroxy bile acids in many species [3]. This enzyme is both a bile salt and a 3-hydroxysteroid sulfotransferase. In addition to the 5β-bile acid glycolithocholate, deoxycholate, 3β-hydroxy-5-cholenoate and dehydroepiandrosterone (3β-hydroxyandrost-5-en-17-one) also act as substrates [see also EC 2.8.2.2 (alcohol sulfotransferase) and EC 2.8.2.34 (glycochenodeoxycholate sulfotransferase)]. May be identical to EC 2.8.2.2 [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 65802-92-8
References:
1.  Chen, L.-J., Bolt, R.J. and Admirand, W.H. Enzymatic sulfation of bile salts. Partial purification and characterization of an enzyme from rat liver that catalyzes the sulfation of bile salts. Biochim. Biophys. Acta 480 (1977) 219–227. [DOI] [PMID: 831833]
2.  Barnes, S., Waldrop, R., Crenshaw, J., King, R.J. and Taylor, K.B. Evidence for an ordered reaction mechanism for bile salt: 3′phosphoadenosine-5′-phosphosulfate: sulfotransferase from rhesus monkey liver that catalyzes the sulfation of the hepatotoxin glycolithocholate. J. Lipid Res. 27 (1986) 1111–1123. [PMID: 3470420]
3.  Barnes, S., Buchina, E.S., King, R.J., McBurnett, T. and Taylor, K.B. Bile acid sulfotransferase I from rat liver sulfates bile acids and 3-hydroxy steroids: purification, N-terminal amino acid sequence, and kinetic properties. J. Lipid Res. 30 (1989) 529–540. [PMID: 2754334]
4.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [DOI] [PMID: 12543708]
[EC 2.8.2.14 created 1978, modified 2005]
 
 
EC 2.8.2.34     
Accepted name: glycochenodeoxycholate sulfotransferase
Reaction: 3′-phosphoadenylyl sulfate + glycochenodeoxycholate = adenosine 3′,5′-bisphosphate + glycochenodeoxycholate 7-sulfate
For diagram of reaction, click here
Glossary: 3′-phosphoadenylyl sulfate = PAPS
glycochenodeoxycholate 7-sulfate = N-(3α-hydroxy-7α-sulfooxy-5β-cholan-24-oyl)glycine
Other name(s): bile acid:3′-phosphoadenosine-5′-phosphosulfate sulfotransferase; bile acid:PAPS:sulfotransferase; BAST; 3′-phosphoadenylyl-sulfate:glycochenodeoxycholate 7-sulfotransferase
Systematic name: 3′-phosphoadenylyl-sulfate:glycochenodeoxycholate 7-sulfonotransferase
Comments: The enzyme specifically sulfates glycochenodeoxycholate at the 7α-position (see also EC 2.8.2.14 bile-salt sulfotransferase). The monohydroxy bile acids glycolithocholate, chenodeoxycholate and ursodeoxycholate act as inhibitors.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 72668-90-7
References:
1.  Barnes, S., Burhol, P.G., Zander, R., Haggstrom, G., Settine, R.L. and Hirschowitz, B.I. Enzymatic sulfation of glycochenodeoxycholic acid by tissue fractions from adult hamsters. J. Lipid Res. 20 (1979) 952–959. [PMID: 533830]
2.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [DOI] [PMID: 12543708]
[EC 2.8.2.34 created 2005]
 
 
EC 2.8.3.25     
Accepted name: bile acid CoA-transferase
Reaction: (1) lithocholoyl-CoA + cholate = lithocholate + choloyl-CoA
(2) deoxycholoyl-CoA + cholate = deoxycholate + choloyl-CoA
Other name(s): baiF (gene name); baiK (gene name); bile acid coenzyme A transferase
Systematic name: lithocholoyl-CoA:cholate CoA-transferase
Comments: The enzyme, characterized from the gut bacterium Clostridium scindens, catalyses the last step in bile acid 7α-dehydroxylation, the removal of the CoA moiety from the products. By using a transferase rather than hydrolase, the bacteria conserve the thioester bond energy, saving ATP molecules. Clostridium scindens possesses two forms of the enzyme, encoded by the baiF and baiK genes. While the enzymes have a broad acceptor specificity and can use allocholate, ursodeoxycholate, and β-muricholate, the donor specificity is more strict. BaiF acts on lithocholoyl-CoA and deoxycholoyl-CoA, and BaiK acts only on the latter.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Ridlon, J.M. and Hylemon, P.B. Identification and characterization of two bile acid coenzyme A transferases from Clostridium scindens, a bile acid 7α-dehydroxylating intestinal bacterium. J. Lipid Res. 53 (2012) 66–76. [DOI] [PMID: 22021638]
[EC 2.8.3.25 created 2005 as EC 3.1.2.26, transferred 2016 to EC 2.8.3.25]
 
 
EC 3.1.2.26      
Transferred entry: bile-acid-CoA hydrolase. Now EC 2.8.3.25, bile acid CoA transferase
[EC 3.1.2.26 created 2005, deleted 2016]
 
 
EC 3.1.2.27     
Accepted name: choloyl-CoA hydrolase
Reaction: choloyl-CoA + H2O = cholate + CoA
For diagram of the biosynthesis of cholic-acid conjugates, click here
Other name(s): PTE-2 (ambiguous); choloyl-coenzyme A thioesterase; chenodeoxycholoyl-coenzyme A thioesterase; peroxisomal acyl-CoA thioesterase 2
Systematic name: choloyl-CoA hydrolase
Comments: Also acts on chenodeoxycholoyl-CoA and to a lesser extent on short- and medium- to long-chain acyl-CoAs, and other substrates, including trihydroxycoprostanoyl-CoA, hydroxymethylglutaryl-CoA and branched chain acyl-CoAs, all of which are present in peroxisomes. The enzyme is strongly inhibited by CoA and may be involved in controlling CoA levels in the peroxisome [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Hunt, M.C., Solaas, K., Kase, B.F. and Alexson, S.E. Characterization of an acyl-coA thioesterase that functions as a major regulator of peroxisomal lipid metabolism. J. Biol. Chem. 277 (2002) 1128–1138. [DOI] [PMID: 11673457]
2.  Solaas, K., Sletta, R.J., Soreide, O. and Kase, B.F. Presence of choloyl- and chenodeoxycholoyl-coenzyme A thioesterase activity in human liver. Scand. J. Clin. Lab. Invest. 60 (2000) 91–102. [PMID: 10817395]
3.  Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137–174. [DOI] [PMID: 12543708]
[EC 3.1.2.27 created 2005]
 
 
EC 3.5.1.24     
Accepted name: choloylglycine hydrolase
Reaction: glycocholate + H2O = cholate + glycine
For diagram of cholic acid conjugates biosynthesis, click here
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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37289-07-9
References:
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. [DOI] [PMID: 10993]
[EC 3.5.1.24 created 1972]
 
 
EC 3.5.1.74     
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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 125752-75-2
References:
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 3.5.1.74 created 1992]
 
 
EC 6.2.1.7     
Accepted name: cholate—CoA ligase
Reaction: (1) ATP + cholate + CoA = AMP + diphosphate + choloyl-CoA
(2) ATP + (25R)-3α,7α,12α-trihydroxy-5β-cholestan-26-oate + CoA = AMP + diphosphate + (25R)-3α,7α,12α-trihydroxy-5β-cholestanoyl-CoA
For diagram of cholic acid conjugates biosynthesis, click here and for diagram of cholic acid biosynthesis (sidechain), click here
Glossary: cholate = 3α,7α,12α-trihydroxy-5β-cholan-24-oate
trihydroxycoprostanoate = 3α,7α,12α-trihydroxy-5β-cholestan-26-oate
Other name(s): BAL; bile acid CoA ligase; bile acid coenzyme A ligase; choloyl-CoA synthetase; choloyl coenzyme A synthetase; cholic thiokinase; cholate thiokinase; cholic acid:CoA ligase; 3α,7α,12α-trihydroxy-5β-cholestanoyl coenzyme A synthetase; 3α,7α,12α-trihydroxy-5β-cholestanoate-CoA ligase; 3α,7α,12α-trihydroxy-5β-cholestanoate-CoA synthetase; THCA-CoA ligase; 3α,7α,12α-trihydroxy-5β-cholestanate—CoA ligase; 3α,7α,12α-trihydroxy-5β-cholestanate:CoA ligase (AMP-forming); cholyl-CoA synthetase; trihydroxycoprostanoyl-CoA synthetase
Systematic name: cholate:CoA ligase (AMP-forming)
Comments: Requires Mg2+ for activity. The mammalian enzyme is membrane-bound and catalyses the first step in the conjugation of bile acids with amino acids, converting bile acids into their acyl-CoA thioesters. Chenodeoxycholate, deoxycholate, lithocholate and trihydroxycoprostanoate can also act as substrates [7]. The bacterial enzyme is soluble and participates in an anaerobic bile acid 7 α-dehydroxylation pathway [5].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9027-90-1
References:
1.  Elliott, W.H. The enzymic activation of cholic acid by guinea-pig-liver microsomes. Biochem. J. 62 (1956) 427–433. [PMID: 13303991]
2.  Elliott, W.H. The breakdown of adenosine triphosphate accompanying cholic acid activation by guinea-pig liver microsomes. Biochem. J. 65 (1957) 315–321. [PMID: 13403911]
3.  Prydz, K., Kase, B.F., Björkhem, I. and Pedersen, J.I. Subcellular localization of 3α,7α-dihydroxy- and 3α,7α,12α-trihydroxy-5β-cholestanoyl-coenzyme A ligase(s) in rat liver. J. Lipid Res. 29 (1988) 997–1004. [PMID: 3183523]
4.  Schepers, L., Casteels, M., Verheyden, K., Parmentier, G., Asselberghs, S., Eyssen, H.J. and Mannaerts, G.P. Subcellular distribution and characteristics of trihydroxycoprostanoyl-CoA synthetase in rat liver. Biochem. J. 257 (1989) 221–229. [PMID: 2521999]
5.  Mallonee, D.H., Adams, J.L. and Hylemon, P.B. The bile acid-inducible baiB gene from Eubacterium sp. strain VPI 12708 encodes a bile acid-coenzyme A ligase. J. Bacteriol. 174 (1992) 2065–2071. [DOI] [PMID: 1551828]
6.  Wheeler, J.B., Shaw, D.R. and Barnes, S. Purification and characterization of a rat liver bile acid coenzyme A ligase from rat liver microsomes. Arch. Biochem. Biophys. 348 (1997) 15–24. [DOI] [PMID: 9390170]
7.  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]
[EC 6.2.1.7 created 1961 (EC 6.2.1.29 created 1992, incorporated 2005), modified 2005]
 
 
EC 6.2.1.29      
Deleted entry:  3α,7α,12α-trihydroxy-5β-cholestanate—CoA ligase. The enzyme is identical to EC 6.2.1.7, cholate—CoA ligase
[EC 6.2.1.29 created 1992, deleted 2005]
 
 
EC 6.2.1.41     
Accepted name: 3-[(3aS,4S,7aS)-7a-methyl-1,5-dioxo-octahydro-1H-inden-4-yl]propanoate—CoA ligase
Reaction: ATP + 3-[(3aS,4S,7aS)-7a-methyl-1,5-dioxo-octahydro-1H-inden-4-yl]propanoate + CoA = AMP + diphosphate + 3-[(3aS,4S,7aS)-7a-methyl-1,5-dioxo-octahydro-1H-inden-4-yl]propanoyl-CoA
For diagram of cholesterol catabolism, click here
Glossary: 3-[(3aS,4S,7aS)-7a-methyl-1,5-dioxo-octahydro-1H-inden-4-yl]propanoate = HIP
Other name(s): fadD3 (gene name); HIP—CoA ligase
Systematic name: 3-[(3aS,4S,7aS)-7a-methyl-1,5-dioxo-octahydro-1H-inden-4-yl]propanoate:CoA ligase (AMP-forming)
Comments: The enzyme, characterized from actinobacterium Mycobacterium tuberculosis, catalyses a step in the degradation of cholesterol and cholate. The enzyme is very specific for its substrate, and requires that the side chain at C17 is completely removed.
Links to other databases: BRENDA, EAWAG-BBD, EXPASY, KEGG, MetaCyc
References:
1.  Horinouchi, M., Hayashi, T., Koshino, H. and Kudo, T. ORF18-disrupted mutant of Comamonas testosteroni TA441 accumulates significant amounts of 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid and its derivatives after incubation with steroids. J. Steroid Biochem. Mol. Biol. 101 (2006) 78–84. [DOI] [PMID: 16891113]
2.  Casabon, I., Crowe, A.M., Liu, J. and Eltis, L.D. FadD3 is an acyl-CoA synthetase that initiates catabolism of cholesterol rings C and D in actinobacteria. Mol. Microbiol. 87 (2013) 269–283. [DOI] [PMID: 23146019]
[EC 6.2.1.41 created 2014]
 
 


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