The Enzyme Database

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Transferred entry: docosahexaenoic acid ω-hydroxylase. Now EC, docosahexaenoic acid ω-hydroxylase
[EC created 2014, deleted 2018]
Accepted name: docosahexaenoic acid ω-hydroxylase
Reaction: docosahexaenoate + [reduced NADPH—hemoprotein reductase] + O2 = 22-hydroxydocosahexaenoate + [oxidized NADPH—hemoprotein reductase] + H2O
Glossary: docosahexaenoate = (4Z,7Z,10Z,13Z,16Z,19Z)-docosa-4,7,10,13,16,19-hexaenoate
icosapentaenoate = (5Z,8Z,11Z,14Z,17Z)-icosa-5,8,11,14,17-pentaenoate
Other name(s): CYP4F3B; CYP4V2; docosahexaenoate,NADPH:O2 oxidoreductase (22-hydroxydocosahexaenoate forming)
Systematic name: docosahexaenoate,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (22-hydroxydocosahexaenoate-forming)
Comments: A cytochrome P-450 (heme-thiolate) protein isolated from human eye tissue. Defects in the enzyme are associated with Bietti crystalline corneoretinal dystrophy. The enzyme also produces some 21-hydroxydocosahexaenoate. Acts in a similar way on icosapentaenoic acid.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
1.  Nakano, M., Kelly, E.J., Wiek, C., Hanenberg, H. and Rettie, A.E. CYP4V2 in Bietti’s crystalline dystrophy: ocular localization, metabolism of ω-3-polyunsaturated fatty acids, and functional deficit of the p.H331P variant. Mol. Pharmacol. 82 (2012) 679–686. [DOI] [PMID: 22772592]
[EC created 2014 as EC, transferred 2018 to EC]
Accepted name: acyl-CoA 6-desaturase
Reaction: (1) linoleoyl-CoA + 2 ferrocytochrome b5 + O2 + 2 H+ = γ-linolenoyl-CoA + 2 ferricytochrome b5 + 2 H2O
(2) α-linolenoyl-CoA + 2 ferrocytochrome b5 + O2 + 2 H+ = stearidonoyl-CoA + 2 ferricytochrome b5 + 2 H2O
Other name(s): Δ6-desaturase; Δ6-fatty acyl-CoA desaturase; Δ6-acyl CoA desaturase; fatty acid Δ6-desaturase; fatty acid 6-desaturase; linoleate desaturase; linoleic desaturase; linoleic acid desaturase; linoleoyl CoA desaturase; linoleoyl-coenzyme A desaturase; long-chain fatty acid Δ6-desaturase; linoleoyl-CoA,hydrogen-donor:oxygen oxidoreductase; linoleoyl-CoA desaturase; FADS2 (gene name)
Systematic name: acyl-CoA,ferrocytochrome b5:oxygen oxidoreductase (6,7 cis-dehydrogenating)
Comments: An iron protein. The enzyme introduces a cis double bond at carbon 6 of acyl-CoAs. It is a front-end desaturase, introducing the new double bond between a pre-existing double bond and the carboxyl-end of the fatty acid. The human enzyme has a broad substrate range. It also acts on palmitoyl-CoA, generating sapienoyl-CoA [4], and on (9Z,12Z,15Z,18Z,21Z)-tetracosa-9,12,15,18,21-pentaenoyl-CoA, converting it to (6Z,9Z,12Z,15Z,18Z,21Z)-tetracosa-6,9,12,15,18,21-hexaenoyl-CoA as part of a pathway that produces docosahexaenoate [3]. The enzyme contains a cytochrome b5 domain that is assumed to act in vivo as the electron donor to the active site of the desaturase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9082-66-0
1.  Okayasu, T., Nagao, M., Ishibashi, T. and Imai, Y. Purification and partial characterization of linoleoyl-CoA desaturase from rat liver microsomes. Arch. Biochem. Biophys. 206 (1981) 21–28. [DOI] [PMID: 7212717]
2.  Cho, H.P., Nakamura, M.T. and Clarke, S.D. Cloning, expression, and nutritional regulation of the mammalian Δ-6 desaturase. J. Biol. Chem. 274 (1999) 471–477. [DOI] [PMID: 9867867]
3.  Sprecher, H. Metabolism of highly unsaturated n-3 and n-6 fatty acids. Biochim. Biophys. Acta 1486 (2000) 219–231. [DOI] [PMID: 10903473]
4.  Ge, L., Gordon, J.S., Hsuan, C., Stenn, K. and Prouty, S.M. Identification of the Δ-6 desaturase of human sebaceous glands: expression and enzyme activity. J. Invest. Dermatol. 120 (2003) 707–714. [DOI] [PMID: 12713571]
5.  Domergue, F., Abbadi, A., Zähringer, U., Moreau, H. and Heinz, E. In vivo characterization of the first acyl-CoA Δ6-desaturase from a member of the plant kingdom, the microalga Ostreococcus tauri. Biochem. J. 389 (2005) 483–490. [DOI] [PMID: 15769252]
[EC created 1986 as EC, transferred 2000 to EC, modified 2015]

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