In enzymology, Delta24(241)-sterol reductase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are ergosta-5,7,22,24(28)-tetraen-3ò-ol, reduced nicotinamide adenine dinucleotide phosphate (NADPH), and a proton. Its products are ergosterol and oxidised NADP<sup>+</sup>.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is ergosterol:NADP+ Delta24(241)-oxidoreductase. Other names in common use include sterol Delta24(28)-methylene reductase, and sterol Delta24(28)-reductase. This enzyme participates in biosynthesis of steroids.