Catalysis of the reaction: a very-long-chain acyl-CoA + H+ + malonyl-CoA = a very-long-chain 3-oxoacyl-CoA + CO2 + CoA. This reaction is the first (condensation) step of the four-step fatty acid elongation cycle in the endoplasmic reticulum that extends fatty acids of C-16 or longer with an additional 2-C unit. [ http://www.ncbi.nlm.nih.gov/pubmed/19763486 http://www.ncbi.nlm.nih.gov/pubmed/16564093 https://www.rhea-db.org/rhea/32727 ]

Synonyms: very-long-chain beta-ketoacyl-CoA synthase very-long-chain 3-ketoacyl-CoA synthase very-long-chain 3-oxoacyl-CoA synthase elongation of very long chain fatty acids activity ELOVL