Catalyzes the first and rate-limiting reaction of the four reactions that constitute the long-chain fatty acids elongation cycle. This endoplasmic reticulum-bound enzymatic process allows the addition of 2 carbons to the chain of long- and very long-chain fatty acids (VLCFAs) per cycle. Condensing enzyme that catalyzes the synthesis of very long chain saturated (VLC-SFA) and polyunsaturated (PUFA) fatty acids that are involved in multiple biological processes as precursors of membrane lipids and lipid mediators. May play a critical role in early brain and skin development. a very-long-chain acyl-CoA + H(+) + malonyl-CoA = a very-long-chain 3-oxoacyl-CoA + CO2 + CoA H(+) + hexacosanoyl-CoA + malonyl-CoA = 3-oxooctacosanyol-CoA + CO2 + CoA H(+) + malonyl-CoA + octacosanoyl-CoA = 3-oxo-triacontanoyl-CoA + CO2 + CoA H(+) + malonyl-CoA + triacontanoyl-CoA = 3-oxo-dotriacontanoyl-CoA + CO2 + CoA (19Z,22Z,25Z,28Z,31Z)-tetratriacontapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(21Z,24Z,27Z,30Z,33Z)-hexatriacontapentaenoyl-CoA + CO2 + CoA (4Z,7Z,10Z,13Z,16Z,19Z)-docosahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(6Z,9Z,12Z,15Z,18Z,21Z)-tetracosahexaenoyl-CoA + CO2 + CoA (7Z,10Z,13Z,16Z)-docosatetraenoyl-CoA + H(+) + malonyl-CoA = (9Z,12Z,15Z,18Z)-3-oxotetracosatetraenoyl-CoA + CO2 + CoA (11Z,14Z,17Z,20Z,23Z)-hexacosapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(13Z,16Z,19Z,22Z,25Z)-octacosapentaenoyl-CoA + CO2 + CoA (13Z,16Z,19Z,22Z,25Z)-octacosapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(15Z,18Z,21Z,24Z,27Z)-triacontapentaenoyl-CoA + CO2 + CoA (15Z,18Z,21Z,24Z,27Z)-triacontapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(17Z,20Z,23Z,26Z,29Z)-dotriacontapentaenoyl-CoA + CO2 + CoA (17Z,20Z,23Z,26Z,29Z)-dotriacontapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(19Z,22Z,25Z,28Z,31Z)-tetratriacontapentaenoyl-CoA + CO2 + CoA (21Z,24Z,27Z,30Z,33Z)-hexatriacontapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(23Z,26Z,29Z,32Z,35Z)-octatriacontapentaenoyl-CoA + CO2 + CoA (11Z,14Z,17Z,20Z)-hexacosatetraenoyl-CoA + H(+) + malonyl-CoA = (13Z,16Z,19Z,22Z)-3-oxooctacosatetraenoyl-CoA + CO2 + CoA (13Z,16Z,19Z,22Z)-octacosatetraenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(15Z,18Z,21Z,24Z)-triacontatetraenoyl-CoA + CO2 + CoA (15Z,18Z,21Z,24Z)-triacontatetraenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(17Z,20Z,23Z,26Z)-dotriacontatetraenoyl-CoA + CO2 + CoA (17Z,20Z,23Z,26Z)-dotriacontatetraenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(19Z,22Z,25Z,28Z)-tetratriacontatetraenoyl-CoA + CO2 + CoA (19Z,22Z,25Z,28Z)-tetratriacontatetraenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(21Z,24Z,27Z,30Z)-hexatriacontatetraenoyl-CoA + CO2 + CoA (21Z,24Z,27Z,30Z)-hexatriacontatetraenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(23Z,26Z,29Z,32Z)-octatriacontatetraenoyl-CoA + CO2 + CoA (6Z,9Z,12Z,15Z,18Z,21Z)-tetracosahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(8Z,11Z,14Z,17Z,20Z,23Z)-hexacosahexaenoyl-CoA + CO2 + CoA (8Z,11Z,14Z,17Z,20Z,23Z)-hexacosahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(10Z,13Z,16Z,19Z,22Z,25Z)-octacosahexaenoyl-CoA + CO2 + CoA (10Z,13Z,16Z,19Z,22Z,25Z)-octacosahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(12Z,15Z,18Z,21Z,24Z,27Z)-triacontahexaenoyl-CoA + CO2 + CoA (12Z,15Z,18Z,21Z,24Z,27Z)-triacontahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(14Z,17Z,20Z,23Z,26Z,29Z)-dotriacontahexaenoyl-CoA + CO2 + CoA (14Z,17Z,20Z,23Z,26Z,29Z)-dotriacontahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(16Z,19Z,22Z,25Z,28Z,31Z)-tetratriacontahexaenoyl-CoA + CO2 + CoA (16Z,19Z,22Z,25Z,28Z,31Z)-tetratriacontahexaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(18Z,21Z,24Z,27Z,30Z,33Z)-hexatriacontahexaenoyl-CoA + CO2 + CoA (9Z,12Z,15Z,18Z,21Z)-tetracosapentaenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(11Z,14Z,17Z,20Z,23Z)-hexacosapentaenoyl-CoA + CO2 + CoA Lipid metabolism; fatty acid biosynthesis. Oligomer. Expressed in the retina, exclusively in photoreceptor cells and in the brain, skin, testis and lens. Expressed in the ocular tissues of the retina at 10.5 dpc and becomes restricted predominantly to the photoreceptor layer in the mature retina (at protein level). Expressed in the embryo at 7 dpc. The C-terminal di-lysine motif confers endoplasmic reticulum localization. N-glycosylated. Rod or cone-specific conditional knockout of Elovl4 results in a decrease in very long chain (C30-C34) polyunsaturated fatty acids in the retina, but has no effect on photoreceptors survival, phototransduction, synaptic transmission or visual behavior. Belongs to the ELO family. ELOVL4 subfamily.