Involved in the final reduction of the elongation cycle of fatty acid synthesis (FAS II). Catalyzes the reduction of a carbon-carbon double bond in an enoyl moiety that is covalently linked to an acyl carrier protein (ACP). It can use both crotonyl-CoA and trans-2-decenoyl-ACP. It is able to convert trans-2-enoyl-ACP of different length (C2 to C16) to the corresponding acyl-ACP. 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 Not sensitive to tricolsan. Lipid metabolism; fatty acid biosynthesis. Monomer. Cells lacking this gene produce significantly more unsaturated fatty acids than wild-type. The ratio of unsaturated fatty acids to saturated fatty acids in wild-type is 0.76, whereas in the fabV mutant this ratio is increased to 1.12. The major unsaturated fatty acid is the C16:1. When triclosan is added to the reaction mixture, the reductase activity decreases to 15% of the untreated wild-type. Belongs to the TER reductase family.