Biology:Methylsterol monooxygenase

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Short description: Class of enzymes
Methylsterol monooxygenase
Identifiers
EC number1.14.13.72
CAS number37256-80-7
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum

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).[1][2][3][4][5][6][7] This enzyme catalyses the following chemical reaction

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

Methylsterol monooxygenase requires cytochrome b5.

References

  1. "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. July 1997. doi:10.1006/bbrc.1997.6974. PMID 9240456. 
  2. "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. June 1993. PMID 8505296. 
  3. "Affinity chromatography of microsomal enzymes on immobilized detergent-solubilized cytochrome b5". The Journal of Biological Chemistry 261 (8): 3790–9. March 1986. PMID 3949790. 
  4. "Total enzymic synthesis of cholesterol from lanosterol. Cytochrome b5-dependence of 4-methyl sterol oxidase". The Journal of Biological Chemistry 256 (10): 4822–6. May 1981. PMID 7228857. 
  5. "Mixed function oxidases in sterol metabolism. Source of reducing equivalents". The Journal of Biological Chemistry 255 (22): 10624–9. November 1980. PMID 7430141. 
  6. "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. October 1968. PMID 4234469. 
  7. "Investigation of the component reactions of oxidative sterol demethylation. Study of the aerobic and anaerobic processes". Biochemistry 6 (9): 2673–8. September 1967. doi:10.1021/bi00861a005. PMID 4383278. 

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