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Methylsterol monooxygenase (EC 1.14.13.72, methylsterol hydroxylase, 4-methylsterol oxidase, 4,4-dimethyl-5alpha-cholest-7-en-3beta-ol,hydrogen-donor:oxygen oxidoreductase (hydroxylating)) is an enzyme with systematic name 4,4-dimethyl-5alpha-cholest-7-en-3beta-ol,NAD(P)H:oxygen oxidoreductase (hydroxylating). This enzyme catalyses the following chemical reaction

4,4-dimethyl-5alpha-cholest-7-en-3beta-ol + 3 NAD(P)H + 3 H + 3 O₂ ${\displaystyle \rightleftharpoons }$ 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + 3 NAD(P) + 4 H₂O (overall reaction)

(1a) 4,4-dimethyl-5alpha-cholest-7-en-3beta-ol + NAD(P)H + H + O₂ ${\displaystyle \rightleftharpoons }$ 4beta-hydroxymethyl-4alpha-methyl-5alpha-cholest-7-en-3beta-ol + NAD(P) + H₂O

(1b) 4beta-hydroxymethyl-4alpha-methyl-5alpha-cholest-7-en-3beta-ol + NAD(P)H + H + O₂ ${\displaystyle \rightleftharpoons }$ 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + NAD(P) + 2 H₂O

(1c) 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + NAD(P)H + H + O₂ ${\displaystyle \rightleftharpoons }$ 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + NAD(P) + H₂O

Methylsterol monooxygenase requires cytochrome b5.

References

1. Rahier A, Smith M, Taton M (July 1997). "The role of cytochrome b5 in 4alpha-methyl-oxidation and C5(6) desaturation of plant sterol precursors". Biochemical and Biophysical Research Communications. 236 (2): 434–7. doi:10.1006/bbrc.1997.6974. PMID 9240456.
2. Pascal S, Taton M, Rahier A (June 1993). "Plant sterol biosynthesis. Identification and characterization of two distinct microsomal oxidative enzymatic systems involved in sterol C4-demethylation". The Journal of Biological Chemistry. 268 (16): 11639–54. PMID 8505296.
3. Kawata S, Trzaskos JM, Gaylor JL (March 1986). "Affinity chromatography of microsomal enzymes on immobilized detergent-solubilized cytochrome b5". The Journal of Biological Chemistry. 261 (8): 3790–9. PMID 3949790.
4. Fukushima H, Grinstead GF, Gaylor JL (May 1981). "Total enzymic synthesis of cholesterol from lanosterol. Cytochrome b5-dependence of 4-methyl sterol oxidase". The Journal of Biological Chemistry. 256 (10): 4822–6. PMID 7228857.
5. Brady DR, Crowder RD, Hayes WJ (November 1980). "Mixed function oxidases in sterol metabolism. Source of reducing equivalents". The Journal of Biological Chemistry. 255 (22): 10624–9. PMID 7430141.
6. Gaylor JL, Mason HS (October 1968). "Investigation of the component reactions of oxidative sterol demethylation. Evidence against participation of cytochrome P-450". The Journal of Biological Chemistry. 243 (19): 4966–72. PMID 4234469.
7. Miller WL, Kalafer ME, Gaylor JL, Delwiche CV (September 1967). "Investigation of the component reactions of oxidative sterol demethylation. Study of the aerobic and anaerobic processes". Biochemistry. 6 (9): 2673–8. doi:10.1021/bi00861a005. PMID 4383278.

External links

• Methylsterol+monooxygenase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

• Biology

• EC 1.14.13