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⁺ ${\displaystyle \rightleftharpoons }$ ethyl 3-oxohexanoate + NADPH + H⁺

Thus, the two substrates of this enzyme are ethyl (S)-3-hydroxyhexanoate and NADP⁺, whereas its 3 products are ethyl 3-oxohexanoate, 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.

• Heidlas J, Engel KH, Tressl R (1988). "Purification and characterization of two oxidoreductases involved in the enantioselective reduction of 3-oxo, 4-oxo and 5-oxo esters in baker's yeast". Eur. J. Biochem. 172 (3): 633–9. doi:10.1111/j.1432-1033.1988.tb13936.x. PMID 3280313.