Reaction: 4-methylcholesta-8(9),24-dien-3beta-ol is oxidized to 4-carboxycholesta-8(9),24-dien-3beta-ol
- in pathway: Cholesterol biosynthesis
4-methylcholesta-8(9),24-dien-3beta-ol, NADPH + H+, and O2 react to form 4-carboxycholesta-8(9),24-dien-3beta-ol, NADP+, and H2O. This reaction, in the endoplasmic reticulum, is catalyzed by SC4MOL (C-4 methylsterol oxidase). The human enzyme has been identified based on its sequence similarity to yeast methyl sterol oxidase (ERG25) and the ability of the cloned human gene to rescue ERG25-deficient yeast cells (Li and Kaplan 1996). The mechanism and stoichiometry of the reaction have been inferred from studies of partially purified rat enzyme (Gaylor et al. 1975; Fukushima et al. 1981).
Reaction - small molecule participants:
H2O [cytosol]
NADP+ [cytosol]
4CZYMOL [endoplasmic reticulum membrane]
H+ [cytosol]
O2 [cytosol]
NADPH [cytosol]
4MZYMOL [endoplasmic reticulum membrane]
Reactome.org reaction link: R-HSA-194669
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Reaction input - small molecules:
hydron
dioxygen
NADPH(4-)
4-methylzymosterol
Reaction output - small molecules:
water
NADP(3-)
4-carboxyzymosterol
Reactome.org link: R-HSA-194669