Reaction: a 3β-hydroxysteroid + NADP+ = a 3-oxosteroid + NADPH + H+
For diagram of reaction, click here
Other name(s): 3-keto-steroid reductase; 3-KSR; HSD17B7 (gene name); ERG27 (gene name)
Systematic name: 3β-hydroxysteroid:NADP+ 3-oxidoreductase
Comments: The enzyme acts on multiple 3β-hydroxysteroids. Participates in the biosynthesis of zemosterol and cholesterol, where it catalyses the reaction in the opposite direction to that shown. The mammalian enzyme is bifunctional and also catalyses EC 1.1.1.62, 17β-estradiol 17-dehydrogenase [4].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 42616-29-5
References:
1. Swindell, A.C. and Gaylor, J.L. Investigation of the component reactions of oxidative sterol demethylation. Formation and metabolism of 3-ketosteroid intermediates. J. Biol. Chem. 243 (1968) 5546-5555. [PMID: 4387005]
2. Billheimer, J.T., Alcorn, M. and Gaylor, J.L. Solubilization and partial purification of a microsomal 3-ketosteroid reductase of cholesterol biosynthesis. Purification and properties of 3β-hydroxysteroid dehydrogenase and Δ5-3-ketosteroid isomerase from bovine corpora lutea. Arch. Biochem. Biophys. 211 (1981) 430-438. [PMID: 6946726]
3. Gachotte, D., Sen, S.E., Eckstein, J., Barbuch, R., Krieger, M., Ray, B.D. and Bard, M. Characterization of the Saccharomyces cerevisiae ERG27 gene encoding the 3-keto reductase involved in C-4 sterol demethylation. Proc. Natl. Acad. Sci. USA 96 (1999) 12655-12660. [PMID: 10535978]
4. Marijanovic, Z., Laubner, D., Moller, G., Gege, C., Husen, B., Adamski, J. and Breitling, R. Closing the gap: identification of human 3-ketosteroid reductase, the last unknown enzyme of mammalian cholesterol biosynthesis. Mol. Endocrinol. 17 (2003) 1715-1725. [PMID: 12829805]