Molecular function

Catalysis of the reaction: a very-long-chain 2,3-saturated fatty acyl-CoA + NADP+ = a very-long-chain (2E)-enoyl-CoA + H+ + NADPH. This reaction is the fourth (reduction) 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.