Accepted name: acyl-lipid (8-3)-desaturase
Reaction: (1) an (8Z,11Z,14Z)-icosa-8,11,14-trienoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = a (5Z,8Z,11Z,14Z)-icosatetra-5,8,11,14-tetraenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H2O
(2) an (8Z,11Z,14Z,17Z)-icosa-8,11,14,17-tetraenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = a (5Z,8Z,11Z,14Z,17Z)-icosa-5,8,11,14,17-pentaenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H2O
Glossary: (8Z,11Z,14Z)-icosa-8,11,14-trienoate = di-homo-γ-linolenate
(5Z,8Z,11Z,14Z)-icosa-8,11,14-trienoate = arachidonate
Other name(s): acyl-lipid 5-desaturase; Δ5-fatty-acid desaturase; DES5 (gene name); D5des (gene name); FADS1
Systematic name: Δ8 acyl-lipid,ferrocytochrome b5:oxygen oxidoreductase (5,6 cis-dehydrogenating)
Comments: The enzyme, which has been characterized from multiple organisms including the moss Physcomitrella patens, the marine microalga Rebecca salina, and the filamentous fungus Mortierella alpina, introduces a cis double bond at the 5-position in 20-carbon polyunsaturated fatty acids incorporated in a glycerolipid that contain a Δ8 double bond. The enzyme contains a cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase, and does not require an external cytochrome.
1.  Michaelson, L.V., Lazarus, C.M., Griffiths, G., Napier, J.A. and Stobart, A.K. Isolation of a Δ5-fatty acid desaturase gene from Mortierella alpina. J. Biol. Chem. 273 (1998) 19055–19059. [PMID: 9668087]
2.  Kaewsuwan, S., Cahoon, E.B., Perroud, P.F., Wiwat, C., Panvisavas, N., Quatrano, R.S., Cove, D.J. and Bunyapraphatsara, N. Identification and functional characterization of the moss Physcomitrella patens Δ5-desaturase gene involved in arachidonic and eicosapentaenoic acid biosynthesis. J. Biol. Chem. 281 (2006) 21988–21997. [PMID: 16728405]
3.  Zhou, X.R., Robert, S.S., Petrie, J.R., Frampton, D.M., Mansour, M.P., Blackburn, S.I., Nichols, P.D., Green, A.G. and Singh, S.P. Isolation and characterization of genes from the marine microalga Pavlova salina encoding three front-end desaturases involved in docosahexaenoic acid biosynthesis. Phytochemistry 68 (2007) 785–796. [PMID: 17291553]
[EC created 2015]