Catalyzes the first and rate-limiting reaction of the four reactions that constitute the long-chain fatty acids elongation cycle (PubMed:26214738). This process allows the addition of 2 carbons to the chain of long- and very long-chain fatty acids (VLCFAs) per cycle (PubMed:26214738). Condensing enzyme that elongates fatty acids with 12, 14 and 16 carbons with higher activity toward C16:0 acyl-CoAs (By similarity). Catalyzes the synthesis of unsaturated C16 long chain fatty acids and, to a lesser extent, C18:0 and those with low desaturation degree (By similarity). May participate in the production of saturated and monounsaturated VLCFAs of different chain lengths that are involved in multiple biological processes as precursors of membrane lipids and lipid mediators (By similarity). a very-long-chain acyl-CoA + H(+) + malonyl-CoA = a very-long-chain 3-oxoacyl-CoA + CO2 + CoA H(+) + hexadecanoyl-CoA + malonyl-CoA = 3-oxooctadecanoyl-CoA + CO2 + CoA Lipid metabolism; fatty acid biosynthesis. Detected in the CNS (central nervous system) of third larval instar (at protein level) (PubMed:17666430). Expressed in cyst progenitor cells (at protein level) (PubMed:17666430). In the adult fly, expressed in several tissues including, sperm, follicular epithelium, nurse cells and cyst cells (PubMed:17666430). During embryogenesis, expressed in early cellular blastoderm, involuting mesoderm, invaginating foregut, hindgut, in the CNS (central nervous system) and PNS (peripheral nervous system) during organogenesis, and imaginal disks (PubMed:17666430). In cyst cells, expression is restricted to post-meiotic stages during spermatid differentiation (PubMed:17666430). RNAi-mediated knockdown in larvae confers resistance to tunicamycin (PubMed:30081392). RNAi-mediated knockdown reduces ER stress response caused by the accumulation of unfolded protein in the ER by reducing Ire1 and PEK/PERK signaling (PubMed:30081392). RNAi-mediated knockdown in imaginal disks results in lethality (PubMed:17666430). RNAi-mediated knockdown in cyst cells results in abnormal sperm cell development with abnormal organization of individualization cones (PubMed:17666430). Belongs to the ELO family. ELOVL6 subfamily. Probable cloning artifact.