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 exhibits activity toward saturated and monounsaturated acyl-CoA substrates, with the highest activity towards C22:0 acyl-CoA. May participate in the production of both saturated and monounsaturated VLCFAs of different chain lengths that are involved in multiple biological processes as precursors of membrane lipids and lipid mediators. Important for saturated C24:0 and monounsaturated C24:1 sphingolipid synthesis. Indirectly inhibits RPE65 via production of VLCFAs. a very-long-chain acyl-CoA + H(+) + malonyl-CoA = a very-long-chain 3-oxoacyl-CoA + CO2 + CoA eicosanoyl-CoA + H(+) + malonyl-CoA = 3-oxodocosanoyl-CoA + CO2 + CoA docosanoyl-CoA + H(+) + malonyl-CoA = 3-oxotetracosanoyl-CoA + CO2 + CoA H(+) + malonyl-CoA + tetracosanoyl-CoA = 3-oxohexacosanoyl-CoA + CO2 + CoA (11Z)-eicosenoyl-CoA + H(+) + malonyl-CoA = (13Z)-3-oxodocosenoyl-CoA + CO2 + CoA (13Z)-docosenoyl-CoA + H(+) + malonyl-CoA = (15Z)-3-oxotetracosenoyl-CoA + CO2 + CoA Lipid metabolism; fatty acid biosynthesis. Interacts with LASS2, TECR and HSD17B12. Expressed in a broad variety of tissues. Highly expressed in stomach, lung, kidney, skin and intestine. Moderately expressed in white adipose tissue, liver, spleen, brain, brown adipose tissue, heart and muscle. Weakly expressed in testis. The C-terminal di-lysine motif may confer endoplasmic reticulum localization. Homozygous knockout mice die within one day after birth (PubMed:23689133). Death is caused by a skin barrier deficiency and excessive water loss that are associated with impaired formation of lipid lamellae in the stratum corneum (PubMed:23689133). In the epidermis, the levels of ceramides with fatty acid chains containing more than 26 carbons are decreased, while the levels of ceramides with less than 24 carbons are increased (PubMed:23689133). Belongs to the ELO family. ELOVL1 subfamily. The substrate specificity could be slightly different compared to human ELOVL1, AC Q9BW60. No activity toward octadecanoyl-CoA, for instance, is observed in vivo (PubMed:23689133).