Enoyl-ACP reductase of the type II fatty acid syntase (FAS-II) system, which is involved in the biosynthesis of mycolic acids, a major component of mycobacterial cell walls. Catalyzes the NADH-dependent reduction of the double bond of 2-trans-enoyl-[acyl-carrier protein], an essential step in the fatty acid elongation cycle of the FAS-II pathway. Shows preference for long-chain fatty acyl thioester substrates, and can also use 2-trans-enoyl-CoAs as alternative substrates. The mycobacterial FAS-II system utilizes the products of the FAS-I system as primers to extend fatty acyl chain lengths up to C56, forming the meromycolate chain that serves as the precursor for final mycolic acids. a 2,3-saturated acyl-[ACP] + NAD(+) = a (2E)-enoyl-[ACP] + H(+) + NADH a 2,3-saturated acyl-CoA + NAD(+) = a (2E)-enoyl-CoA + H(+) + NADH Lipid metabolism; mycolic acid biosynthesis. Homodimer. Homotetramer. Belongs to the short-chain dehydrogenases/reductases (SDR) family. FabI subfamily.