This entry includes a group of 3-keto-steroid reductases, including 17beta-HSD7 (or HSD17B7) from animals and Erg27 from fungi. 3-keto steroid reductase (in concert with other enzymes) catalyzes NADP-dependent sterol C-4 demethylation, as part of steroid biosynthesis. 3-keto reductase is a classical short-chain dehydrogenase/reductase (SDR), with a well conserved canonical active site tetrad and fairly well conserved characteristic NAD-binding motif [, ]. HSD17B7 is the orthologue of the yeast steroid-3-ketoreductase (Erg27), an enzyme of ergosterol biosynthesis []. HSD17B7 catalyses the conversion of estrone (a 17beta-hydroxysteroid) to the biologically active estradiol [, , ]. Similar to Erg27, it also acts as a 3-ketosteroid reductase [].In humans, predominant expression of 17beta-HSD7 is found not only in reproductive tissues (breast, ovary, placenta) but also in liver and developing brain, principal sites of cholesterol synthesis in keeping with the bifunctional nature of this enzyme [, ].
