The Enzyme Database

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Transferred entry: phosphatidylcholine 12-monooxygenase. Now classified as EC, phosphatidylcholine 12-monooxygenase.
[EC created 1984, deleted 2015]
Accepted name: phosphatidylcholine 12-monooxygenase
Reaction: a 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine + 2 ferrocytochrome b5 + O2 + 2 H+ = a 1-acyl-2-[(12R)-12-hydroxyoleoyl]-sn-glycero-3-phosphocholine + 2 ferricytochrome b5 + H2O
Glossary: ricinoleic acid = (9Z,12R)-12-hydroxyoctadec-9-enoic acid
Other name(s): ricinoleic acid synthase; oleate Δ12-hydroxylase; oleate Δ12-monooxygenase
Systematic name: 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine,ferrocytochrome-b5:oxygen oxidoreductase (12-hydroxylating)
Comments: The enzyme, characterized from the plant Ricinus communis (castor bean), is involved in production of the 12-hydroxylated fatty acid ricinoleate. The enzyme, which shares sequence similarity with fatty-acyl desaturases, requires a cytochrome b5 as the electron donor.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 77950-95-9
1.  Galliard, T. and Stumpf, P.K. Fat metabolism in higher plants. 30. Enzymatic synthesis of ricinoleic acid by a microsomal preparation from developing Ricinus communis seeds. J. Biol. Chem. 241 (1966) 5806–5812. [PMID: 4289003]
2.  Moreau, R.A. and Stumpf, P.K. Recent studies of the enzymic-synthesis of ricinoleic acid by developing castor beans. Plant Physiol. 67 (1981) 672–676. [PMID: 16661734]
3.  Smith, M.A., Jonsson, L., Stymne, S. and Stobart, K. Evidence for cytochrome b5 as an electron donor in ricinoleic acid biosynthesis in microsomal preparations from developing castor bean (Ricinus communis L.). Biochem. J. 287 (1992) 141–144. [PMID: 1417766]
4.  Lin, J.T., McKeon, T.A., Goodrich-Tanrikulu, M. and Stafford, A.E. Characterization of oleoyl-12-hydroxylase in castor microsomes using the putative substrate, 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine. Lipids 31 (1996) 571–577. [DOI] [PMID: 8784737]
5.  Broun, P. and Somerville, C. Accumulation of ricinoleic, lesquerolic, and densipolic acids in seeds of transgenic Arabidopsis plants that express a fatty acyl hydroxylase cDNA from castor bean. Plant Physiol. 113 (1997) 933–942. [PMID: 9085577]
[EC created 1984 as EC, transferred 2015 to EC]
Accepted name: phospholipid:diacylglycerol acyltransferase
Reaction: phospholipid + 1,2-diacyl-sn-glycerol = lysophospholipid + triacylglycerol
Glossary: ricinoleic acid = (9Z,12R)-12-hydroxyoctadec-9-enoic acid
vernolic acid = (9Z,12S,13R)-12,13-epoxyoctadec-9-enoic acid
Other name(s): PDAT
Systematic name: phospholipid:1,2-diacyl-sn-glycerol O-acyltransferase
Comments: This enzyme differs from EC, diacylglycerol O-acyltransferase, by synthesising triacylglycerol using an acyl-CoA-independent mechanism. The specificity of the enzyme for the acyl group in the phospholipid varies with species, e.g., the enzyme from castor bean (Ricinus communis) preferentially incorporates vernoloyl (12,13-epoxyoctadec-9-enoyl) groups into triacylglycerol, whereas that from the hawk’s beard (Crepis palaestina) incorporates both ricinoleoyl (12-hydroxyoctadec-9-enoyl) and vernoloyl groups. The enzyme from the yeast Saccharomyces cerevisiae specifically transfers acyl groups from the sn-2 position of the phospholipid to diacylglycerol, thus forming an sn-1-lysophospholipid.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 288587-47-3
1.  Dahlqvist, A., Stähl, U., Lenman, M., Banas, A., Lee, M., Sandager, L., Ronne, H. and Stymne, S. Phospholipid:diacylglycerol acyltransferase: An enzyme that catalyzes the acyl-CoA-independent formation of triacylglycerol in yeast and plants. Proc. Natl. Acad. Sci. USA 97 (2000) 6487–6492. [DOI] [PMID: 10829075]
[EC created 2001]

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