This is the first component of the elongase, a microsomal protein complex responsible for extending palmitoyl-CoA and stearoyl-CoA (and modified forms thereof) to very-long-chain acyl CoAs. Multiple forms exist with differing preferences for the substrate, and thus the specific form expressed determines the local composition of very-long-chain fatty acids [6,7]. For example, the FAE1 form from the plant Arabidopsis thaliana accepts only 16 and 18 carbon substrates, with oleoyl-CoA (18:1) being the preferred substrate [5], while CER6 from the same plant prefers substrates with chain length of C22 to C32 [4,8]. cf. EC
1.1.1.330, very-long-chain 3-oxoacyl-CoA reductase, EC
4.2.1.134, very-long-chain (3R)-3-hydroxyacyl-[acyl-carrier protein] dehydratase, and EC
1.3.1.93, very-long-chain enoyl-CoA reductase