enzymology Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

, a Δ⁷-sterol 5(6)-desaturase () is an enzyme that

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the chemical reaction Δ⁷-sterol + 2 ferrocytochrome b₅ + + 2 H⁺ = Δ^5,7-sterol + 2 ferricytochrome b₅ + 2 The four substrates of this enzyme are Δ⁷-sterol, ferrocytochrome b₅, H⁺, and O₂. Its three products are Δ^5,7-sterol, ferricytochrome b₅, and H₂O.

Classification

This enzyme is one of

C-5 sterol desaturase C-5 sterol desaturase (also known as sterol C-5 desaturase and C5SD) is an enzyme that is highly conserved among eukaryotes and catalyzes the dehydrogenation of a C-5(6) bond in a sterol intermediate compound as a step in the biosynthesis of major ...

s, belongs to the family of oxidoreductases, specifically those acting on paired donors, with O₂ as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O₂. With oxidation of a pair of donors resulting in the reduction of molecular oxygen to two molecules of water.

Nomenclature

The systematic name of this enzyme class is Δ⁷-sterol,ferrocytochrome b5:oxygen oxidoreductase 5,6-dehydrogenating. Other names in common use include: * lathosterol oxidase * Δ⁷-sterol Δ⁵-dehydrogenase * Δ⁷-sterol 5-desaturase * Δ⁷-sterol-C5(6)-desaturase * 5-DES Gene names: * SC5D (vertebrates) *

ERG3 ERG3 or sterol C-5 desaturase is a fungal enzyme originally from '' Saccharomyces cerevisiae'', the human ortholog of ERG3 is SC5D. ERG3 localizes to both the endoplasmic reticulum and vesicles, catalyzes the C5(6)-dehydrogenation of episterol ...

(yeast)

Biological role

This enzyme participates in

biosynthesis of steroids A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

History

Previously, this enzyme was known under the name lathosterol oxidase and (), and the entry is now transferred. The following incorrect reaction was suggested:

5α-cholest-7-en-3β-ol + NAD(P)H + H⁺ + O₂

\rightleftharpoons

cholesta-5,7-dien-3β-ol + NAD(P)+ + 2 H₂O

The substrates of this enzyme were listed as 5α-cholest-7-en-3β-ol, NAD(P)H, H⁺, and O₂. Its products were listed as cholesta-5,7-dien-3β-ol (provitamin D₃), NAD⁺ or NADP⁺, and H₂O. It was stated that the enzyme has two

cofactors Cofactor may also refer to: * Cofactor (biochemistry), a substance that needs to be present in addition to an enzyme for a certain reaction to be catalysed * A domain parameter in elliptic curve cryptography, defined as the ratio between the order ...

FAD A fad or trend is any form of collective behavior that develops within a culture, a generation or social group in which a group of people enthusiastically follow an impulse for a short period. Fads are objects or behaviors that achieve short- ...

, and FMN.

References

* * * * EC 1.14.21 NADPH-dependent enzymes NADH-dependent enzymes Flavoproteins Enzymes of unknown structure {{1.14-enzyme-stub

Classification

Nomenclature

Biological role

History

See also

References