Involved in the fatty acid synthesis (FAS II). Catalyzes the reduction of a carbon-carbon double bond in an enoyl moiety that is covalently linked to a coenzyme A (CoA). a 2,3-saturated acyl-CoA + NAD(+) = a (2E)-enoyl-CoA + H(+) + NADH Lipid metabolism; fatty acid biosynthesis. Monomer. Belongs to the TER reductase family.