Cholest-5-ene-3beta,7alpha-diol 3beta-dehydrogenase

In enzymology, a cholest-5-ene-3β,7α-diol 3β-dehydrogenase () is an enzyme that catalyzes several chemical reactions of steroids.

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. The human version of this enzyme is known as hydroxy-Δ-5-steroid dehydrogenase, 3 β- and steroid delta-isomerase 7 or HSD3B7 which is encoded by the HSD3B7 gene.

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