In enzymology, a Delta14-sterol reductase (EC 1.3.1.70) is an enzyme that catalyzes the chemical reaction

4,4-dimethyl-5alpha-cholesta-8,24-dien-3beta-ol + NADP⁺ ${\displaystyle \rightleftharpoons }$ 4,4-dimethyl-5alpha-cholesta-8,14,24-trien-3beta-ol + NADPH + H⁺

Thus, the two substrates of this enzyme are 4,4-dimethyl-5alpha-cholesta-8,24-dien-3beta-ol and NADP⁺, whereas its 3 products are 4,4-dimethyl-5alpha-cholesta-8,14,24-trien-3beta-ol, NADPH, and H⁺.

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 4,4-dimethyl-5alpha-cholesta-8,24-dien-3beta-ol:NADP+ Delta14-oxidoreductase. This enzyme participates in biosynthesis of steroids.

• Bottema CK, Parks LW (1978). "Delta14-sterol reductase in Saccharomyces cerevisiae". Biochim. Biophys. Acta. 531 (3): 301–7. doi:10.1016/0005-2760(78)90212-6. PMID 32908.
• Paik YK, Trzaskos JM, Shafiee A, Gaylor JL (1984). "Microsomal enzymes of cholesterol biosynthesis from lanosterol Characterization, solubilization, and partial purification of NADPH-dependent delta 8,14-steroid 14-reductase". J. Biol. Chem. 259 (21): 13413–23. PMID 6444198.