Component of a microsomal membrane bound medium-chain fatty acid elongation system, which extends medium-chain-length fatty acids to long-chain fatty acids. Component of elongase I, which extends 12-16-carbon fatty acyl-CoAs such as lauroyl-CoA to 14-18-carbon fatty acids by incorporation of malonyl-CoA. a very-long-chain acyl-CoA + H(+) + malonyl-CoA = a very-long-chain 3-oxoacyl-CoA + CO2 + CoA H(+) + malonyl-CoA + tetradecanoyl-CoA = 3-oxohexadecanoyl-CoA + CO2 + CoA (9Z)-tetradecenoyl-CoA + H(+) + malonyl-CoA = 3-oxo-(11Z)-hexadecenoyl-CoA + CO2 + CoA Induced in wild-type cells supplemented with 14:0 fatty acids and repressed when cells are supplied with 16- and 18-carbon fatty acids. The C-terminal di-lysine 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 937 molecules/cell in log phase SD medium. Belongs to the ELO family.