In enzymology, a (S)-3-hydroxyacid-ester dehydrogenase (EC 1.1.1.280) is an enzyme that catalyzes the chemical reaction ethyl (S)-3-hydroxyhexanoate + NADP+ ethyl 3-oxohexanoate + NADPH + H+ Thus, the two substrates of this enzyme are and NADP+, whereas its 3 products are , NADPH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is ethyl-(S)-3-hydroxyhexanoate:NADP+ 3-oxidoreductase. This enzyme is also called 3-oxo ester (S)-reductase.