7-Dehydrocholesterol reductase, also known as DHCR7, is a protein that in humans is encoded by the DHCR7 gene.
The protein encoded by this gene is an enzyme catalyzing the reversible production of cholesterol from 7-dehydrocholesterol using nicotinamide adenine dinucleotide phosphate (NADPH) as its cofactor.
The DHCR7 gene encodes delta-7-sterol reductase (EC 1.3.1.21), the ultimate enzyme of mammalian sterol biosynthesis that converts 7-dehydrocholesterol (7-DHC) to cholesterol. This enzyme removes the C(7âÂÂ8) double bond introduced by the sterol delta8-delta7 isomerases. In addition, its role in drug-induced malformations is known: inhibitors of the last step of cholesterol biosynthesis such as AY9944 and BM15766 severely impair brain development.
It displays a modest level of enzyme promiscuity, being able to catalyze analogous reactions with (substrate in forward direction) brassicasterol, 20S(OH)7DHC, 27(OH)DHC and 7-dehydrodesmosterol.
A deficiency is associated with SmithâÂÂLemliâÂÂOpitz syndrome.
All house cats and dogs have higher-than-usual activity of this enzyme, causing an inability to synthesize vitamin D due to the lack of 7-dehydrocholesterol.