3-Ketosteroid reductase

In enzymology, 3-keto-steroid reductase is an enzyme that catalyzes the reduction of keto sterols to the corresponding 3β-hydroxysteroids. For example:
In this example, the two substrates of the enzyme are lophenol and oxidised nicotinamide adenine dinucleotide phosphate. Its products are 4α-methyllathosterone, reduced NADPH, and a proton.
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 3beta-hydroxy-steroid:NADP⁺ 3-oxidoreductase. This enzyme is also called 3-KSR. This enzyme participates in biosynthesis of steroids.