In enzymology, a ÃÂ<sup>7</sup>-sterol 5(6)-desaturase () is an enzyme that catalyzes the chemical reaction
ÃÂ<sup>7</sup>-sterol + 2 ferrocytochrome b<sub>5</sub> + + 2 H<sup>+</sup> = ÃÂ<sup>5,7</sup>-sterol + 2 ferricytochrome b<sub>5</sub> + 2
This enzyme participates in biosynthesis of steroids; in vertebrates the pathway leads to cholesterol. The oxidation reaction which it catalyses is:
It uses two molecules of the cofactor ferrocytochrome b<sub>5</sub> with two protons and one oxygen to convert lathosterol to 7-dehydrocholesterol and water. In plants it acts on episterol.
This enzyme is one of C-5 sterol desaturases, belongs to the family of oxidoreductases, specifically those acting on paired donors, with O<sub>2</sub> as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O<sub>2</sub>. With oxidation of a pair of donors resulting in the reduction of molecular oxygen to two molecules of water.
The systematic name of this enzyme class is ÃÂ<sup>7</sup>-sterol,ferrocytochrome b5:oxygen oxidoreductase 5,6-dehydrogenating. Other names in common use include:
Gene names: