7-Dehydrocholesterol reductase

7-Dehydrocholesterol reductase, also known as DHCR7, is a protein that in humans is encoded by the DHCR7 gene.

Function

The protein encoded by this gene is an enzyme catalyzing the reversible production of cholesterol from 7-dehydrocholesterol using nicotinamide adenine dinucleotide phosphate as its cofactor.
The DHCR7 gene encodes delta-7-sterol reductase, the ultimate enzyme of mammalian sterol biosynthesis that converts 7-dehydrocholesterol to cholesterol. This enzyme removes the C 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 brassicasterol, 20S7DHC, 27DHC and 7-dehydrodesmosterol.

A deficiency is associated with Smith–Lemli–Opitz 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.