Methylsterol monooxygenase

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 ⇌ 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 ⇌ 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 ⇌ 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 ⇌ 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + NAD(P)⁺ + H₂O

Methylsterol monooxygenase requires cytochrome b5.