3 beta-hydroxysteroid dehydrogenase type 7 (or 3β-HSD7) is an enzyme that in humans is encoded by the HSD3B7 gene. Also called cholest-5-ene-3β,7α-diol 3β-dehydrogenase (), this enzyme catalyzes several chemical reactions of steroids, and is particularly important for bile acid synthesis which is needed for proper lipid digestion.
The primary reaction is to convert 7α-hydroxycholesterol to 7α-hydroxycholest-4-en-3-one:
The two substrates are 7α-hydroxycholesterol and oxidised nicotinamide adenine dinucleotide (NAD+). The products are 7α-hydroxycholest-4-en-3-one, reduced NADH, and a proton.
The systematic name of this enzyme class is cholest-5-ene-3β,7α-diol:NAD+ 3-oxidoreductase. This enzyme is also called 3β-hydroxy-Δ5-C27-steroid oxidoreductase.
Function
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. This enzyme is involved in the initial stages of the synthesis of bile acids from cholesterol and a member of the short-chain dehydrogenase/reductase superfamily. This enzyme is a membrane-associated endoplasmic reticulum protein which is active against 7-alpha hydroxylated sterol substrates.
Clinical significance
Mutations in the HSD3B7 gene are associated with a congenital bile acid synthesis defect which leads to neonatal cholestasis, a form of progressive liver disease.
See also
3-beta-HSD
References