5β-Reductase, also called Δ4-3-oxosteroid 5β-reductase (), is an enzyme that in humans is encoded by the gene AKC1D1. Its systematic name is 5β-cholestan-3-one:NADP+ 4,5-oxidoreductase.
This enzyme catalyses the following general chemical reaction:
5β-cholestan-3-one + NADP+ cholest-4-en-3-one + NADPH + H+
For example, it interconverts 5β-dihydrocortisone and cortisone:
AKR1D1
Aldo-keto reductase family 1 member D1 (AKR1D1), the sole 5β-Reductase isozyme known in humans, is an enzyme which is humans is encoded by the gene AKR1D1. This enzyme is important for bile acid synthesis and steroid metabolism.
AKR1D1 efficiently acts on bile-acid intermediates, progesterone, 17α-hydroxyprogesterone, androstenedione, and testosterone to transform them into 5β-reduced metabolites. It can also act on aldosterone, corticosterone, and cortisol.
Medical significance Pathogenic mutations in AKR1D1 are associated with a rare type of bile acid synthesis disorder called congenital bile acid synthesis defect 2 (CBAS2).
Other names This enzyme has multiple alternative names, including: 3-oxo-Δ4-steroid 5β-reductase, androstenedione 5β-reductase, cholestenone 5β-reductase, cortisone 5β-reductase, cortisone Δ4-5β-reductase, steroid 5β-reductase, testosterone 5β-reductase, Δ4-3-ketosteroid 5β-reductase, Δ4-5β-reductase, Δ4-hydrogenase, 4,5β-dihydrocortisone:NADP+ Δ4-oxidoreductase, and 3-oxo-5β-steroid:NADP+ Δ4-oxidoreductase.
See also 5α-Reductase Steroidogenic enzyme
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