ENZYME entry: EC 18.104.22.168
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|sterol-4alpha-carboxylate 3-dehydrogenase (decarboxylating).|
|sterol 4alpha-carboxylic decarboxylase.|
- a 3beta-hydroxysteroid-4alpha-carboxylate + NADP(+) <=> a 3-oxosteroid + CO2 + NADPH
- a 3beta-hydroxysteroid-4alpha-carboxylate + NAD(+) <=> a 3-oxosteroid + CO2 + NADH
- The enzyme participates in the biosynthesis of several important
sterols such as ergosterol and cholesterol.
- It is part of a three enzyme system that removes methyl groups from
the C-4 position of steroid molecules.
- The first enzyme, EC 22.214.171.124, catalyzes three successive oxidations
of the methyl group, resulting in a carboxyl group; the second
enzyme, EC 126.96.36.199, catalyzes an oxidative decarboxylation that
results in a reduction of the 3beta-hydroxy group at the C-3 carbon
to an oxo group; and the last enzyme, EC 188.8.131.520, reduces the 3-oxo
group back to a 3beta-hydroxyl.
- If a second methyl group remains at the C-4 position, this enzyme
also catalyzes its epimerization from 4beta to 4alpha orientation,
so it could serve as a substrate for a second round of demethylation.
- Cf. EC 184.108.40.2068.
|PRIAM enzyme-specific profiles||220.127.116.11|
|KEGG Ligand Database for Enzyme Nomenclature||18.104.22.168|
|IUBMB Enzyme Nomenclature||22.214.171.124|
|MEDLINE||Find literature relating to 126.96.36.199|
|Rhea expert-curated reactions||188.8.131.52|
entries corresponding to 1.1.1.-
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