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In enzymology, a Δ7-sterol 5(6)-desaturase (EC 1.14.19.20) is an enzyme that catalyzes the chemical reaction
| Δ7-sterol 5(6)-desaturase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 1.14.19.20 | ||||||||
| CAS no. | 37255-37-1 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| |||||||||
Δ7-sterol + 2 ferrocytochrome b5 + O2 + 2 H+ = Δ5,7-sterol + 2 ferricytochrome b5 + 2 H2O
The four substrates of this enzyme are Δ7-sterol, ferrocytochrome b5, H+, and O2. Its three products are Δ5,7-sterol, ferricytochrome b5, and H2O.
Classification
editThis enzyme is one of C-5 sterol desaturases, 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
editThe 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:
Biological role
editThis enzyme participates in biosynthesis of steroids.
History
editPreviously, this enzyme was known under the name lathosterol oxidase and (EC 1.14.21.6), and the entry is now transferred. The following incorrect reaction was suggested:
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: FAD, and FMN.
See also
editReferences
edit- Dempsey ME, Seaton JD, Schroepfer GJ, Trockman RW (1964). "The Intermediary Role of Δ5,7-cholestadien-3-β-ol in Cholesterol Biosynthesis". J. Biol. Chem. 239: 1381–7. PMID 14189869.
- Nishino H, Nakaya J, Nishi S, Kurosawa T, Ishibashi T (1997). "Temperature-induced differential kinetic properties between an initial burst and the following steady state in membrane-bound enzymes: studies on lathosterol 5-desaturase". Arch. Biochem. Biophys. 339 (2): 298–304. doi:10.1006/abbi.1996.9871. PMID 9056262.
- Taton M, Rahier A (1996). "Plant sterol biosynthesis: identification and characterization of higher plant Δ7-sterol C5(6)-desaturase". Arch. Biochem. Biophys. 325 (2): 279–88. doi:10.1006/abbi.1996.0035. PMID 8561508.
- Taton M, Husselstein T, Benveniste P, Rahier A (2000). "Role of highly conserved residues in the reaction catalyzed by recombinant Δ7-sterol-C5(6)-desaturase studied by site-directed mutagenesis". Biochemistry. 39 (4): 701–11. doi:10.1021/bi991467t. PMID 10651635.
