The Enzyme Database

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EC 1.14.13.72     
Accepted name: methylsterol monooxygenase
Reaction: 4,4-dimethyl-5α-cholest-7-en-3β-ol + 3 NAD(P)H + 3 H+ + 3 O2 = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carboxylate + 3 NAD(P)+ + 4 H2O (overall reaction)
(1a) 4,4-dimethyl-5α-cholest-7-en-3β-ol + NAD(P)H + H+ + O2 = 4β-hydroxymethyl-4α-methyl-5α-cholest-7-en-3β-ol + NAD(P)+ + H2O
(1b) 4β-hydroxymethyl-4α-methyl-5α-cholest-7-en-3β-ol + NAD(P)H + H+ + O2 = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carbaldehyde + NAD(P)+ + 2 H2O
(1c) 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carbaldehyde + NAD(P)H + H+ + O2 = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carboxylate + NAD(P)+ + H2O
For diagram of sterol ring A modification, click here
Other name(s): methylsterol hydroxylase; 4-methylsterol oxidase; 4,4-dimethyl-5α-cholest-7-en-3β-ol,hydrogen-donor:oxygen oxidoreductase (hydroxylating)
Systematic name: 4,4-dimethyl-5α-cholest-7-en-3β-ol,NAD(P)H:oxygen oxidoreductase (hydroxylating)
Comments: Requires cytochrome b5. Also acts on 4α-methyl-5α-cholest-7-en-3β-ol. The sterol can be based on cycloartenol as well as lanosterol.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37256-80-7
References:
1.  Rahier, A., Smith, M. and Taton, M. The role of cytochrome b5 in 4α-methyl-oxidation and C5(6) desaturation of plant sterol precursors. Biochem. Biophys. Res. Commun. 236 (1997) 434–437. [PMID: 9240456]
2.  Pascal, S., Taton, M. and Rahier, A. Plant sterol biosynthesis. Identification and characterization of two distinct microsomal oxidative enzymatic systems involved in sterol C4-demethylation. J. Biol. Chem. 268 (1993) 11639–11654. [PMID: 8505296]
3.  Kawata, S., Trzaskos, J.M. and Gaylor, J.L. Affinity chromatography of microsomal enzymes on immobilized detergent-solubilized cytochrome b5. J. Biol. Chem. 261 (1986) 3790–3799. [PMID: 3949790]
4.  Fukushima, H., Grinstead, G.F. and Gaylor, J.L. Total enzymic synthesis of cholesterol from lanosterol. Cytochrome b5-dependence of 4-methyl sterol oxidase. J. Biol. Chem. 256 (1981) 4822–4826. [PMID: 7228857]
5.  Brady, D.R., Crowder, R.D. and Hayes, W.J. Mixed function oxidases in sterol metabolism. Source of reducing equivalents. J. Biol. Chem. 255 (1980) 10624–10629. [PMID: 7430141]
6.  Gaylor, J.L. and Mason, H.S. Investigation of the component reactions of oxidative sterol demethylation. Evidence against participation of cytochrome P-450. J. Biol. Chem. 243 (1968) 4966–4972. [PMID: 4234469]
7.  Miller, W.L., Kalafer, M.E., Gaylor, J.L. and Delwicke, C.V. Investigation of the component reactions of oxidative sterol demethylation. Study of the aerobic and anaerobic processes. Biochemistry 6 (1967) 2673–2678. [PMID: 4383278]
[EC 1.14.13.72 created 1972 as EC 1.14.99.16, transferred 2002 to EC 1.14.13.72]
 
 


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