EC Explorer

1.14.18.9

4α-methylsterol monooxygenase

4,4-dimethyl-5α-cholest-7-en-3β-ol + 6 ferrocytochrome b₅ + 3 O₂ + 6 H⁺ = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carboxylate + 6 ferricytochrome b₅ + 4 H₂O (overall reaction);;(1a) 4,4-dimethyl-5α-cholest-7-en-3β-ol + 2 ferrocytochrome b₅ + O₂ + 2 H⁺ = 4α-hydroxymethyl-4β-methyl-5α-cholest-7-en-3β-ol + 2 ferricytochrome b₅ + H₂O;;(1b) 4α-hydroxymethyl-4β-methyl-5α-cholest-7-en-3β-ol + 2 ferrocytochrome b₅ + O₂ + 2 H⁺ = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carbaldehyde + 2 ferricytochrome b₅ + 2 H₂O;;(1c) 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carbaldehyde + 2 ferrocytochrome b₅ + O₂ + 2 H⁺ = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carboxylate + 2 ferricytochrome b₅ + H₂O

methylsterol hydroxylase (ambiguous), 4-methylsterol oxidase (ambiguous), 4,4-dimethyl-5α-cholest-7-en-3β-ol,hydrogen-donor:oxygen oxidoreductase (hydroxylating) (ambiguous), methylsterol monooxygenase (ambiguous), ERG25 (gene name), MSMO1 (gene name), 4,4-dimethyl-5α-cholest-7-en-3β-ol,ferrocytochrome-b₅:oxygen oxidoreductase (hydroxylating) (ambiguous)

4,4-dimethyl-5α-cholest-7-en-3β-ol,ferrocytochrome-b₅:oxygen oxidoreductase (C4α-methyl-hydroxylating)

37256-80-7

This enzyme is found in fungi and animals and catalyses a step in the biosynthesis of important sterol molecules such as ergosterol and cholesterol, respectively. The enzyme acts on the 4α-methyl group. Subsequent decarboxylation by EC 1.1.1.170, 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating), occurs concomitantly with epimerization of the remaining 4β-methyl into the 4α position, thus making it a suitable substrate for a second round of catalysis. cf. EC 1.14.13.246, 4β-methylsterol monooxygenase; EC 1.14.18.10, plant 4,4-dimethylsterol C-4α-methyl-monooxygenase; and EC 1.14.18.11, plant 4α-monomethylsterol monooxygenase.

created 1972 as EC 1.14.99.16, transferred 2002 to EC 1.14.13.72, transferred 2017 to EC 1.14.18.9, modified 2019