Component of a microsomal membrane-bound long-chain fatty acid elongation system, which produces the 20-26-carbon very long-chain fatty acids (VLCFA) from long-chain fatty acid precursors and is involved ceramide and inositol sphingolipid biosynthesis. Component of elongase II, which elongates 16-18 carbon fatty acyl-CoAs such as palmitoyl-CoA and stearoyl-CoA to 20-22-carbon fatty acids by incorporation of malonyl-CoA (PubMed:9211877, PubMed:12684876). Involved in the synthesis of 1,3-beta-glucan (PubMed:7768822). The enzymes active site faces the cytosol, whereas VLCFA length is determined by a lysine near the luminal end of transmembrane helix 6 (PubMed:17719544). Plays an important role in lipotoxic cell death induced by oleic acid through maintaining a balanced fatty acid composition in thr plasma membrane (PubMed:29458843). a very-long-chain acyl-CoA + H(+) + malonyl-CoA = a very-long-chain 3-oxoacyl-CoA + CO2 + CoA H(+) + malonyl-CoA + octadecanoyl-CoA = 3-oxoeicosanoyl-CoA + CO2 + CoA H(+) + hexadecanoyl-CoA + malonyl-CoA = 3-oxooctadecanoyl-CoA + CO2 + CoA eicosanoyl-CoA + H(+) + malonyl-CoA = 3-oxodocosanoyl-CoA + CO2 + CoA docosanoyl-CoA + H(+) + malonyl-CoA = 3-oxotetracosanoyl-CoA + CO2 + CoA The C-terminal di-lysine-like motif may confer endoplasmic reticulum localization. The HxxHH motif is essential for ELOp function in vivo and 3-keto acyl-CoA synthase activity in vitro. Present with 3510 molecules/cell in log phase SD medium. Belongs to the ELO family.