Catalyzes the NADPH-dependent reduction of trans-2-enoyl thioesters in mitochondrial fatty acid synthesis (fatty acid synthesis type II). Fatty acid chain elongation in mitochondria uses acyl carrier protein (ACP) as an acyl group carrier, but the enzyme accepts both ACP and CoA thioesters as substrates in vitro. Required for respiration and the maintenance of the mitochondrial compartment. a 2,3-saturated acyl-[ACP] + NADP(+) = a (2E)-enoyl-[ACP] + H(+) + NADPH Homodimer. Belongs to the zinc-containing alcohol dehydrogenase family. Quinone oxidoreductase subfamily.