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ENZYME entry: EC

Accepted Name
3beta-hydroxysteroid-4beta-carboxylate 3-dehydrogenase (decarboxylating)
Reaction catalysed
  • a 3beta-hydroxy-4alpha-methylsteroid-4beta-carboxylate + NAD(+) <=> a 4alpha-methyl-3-oxosteroid + CO2 + NADH
  • a 3beta-hydroxy-4alpha-methylsteroid-4beta-carboxylate + NADP(+) <=> a 4alpha-methyl-3-oxosteroid + CO2 + NADPH
  • This bacterial enzyme participates in the biosynthesis of bacterial sterols.
  • Together with EC (SdmA) it forms an enzyme system that removes one methyl group from the C-4 position of 4,4-dimethylated steroid molecules.
  • SdmA catalyzes three successive oxidations of the C-4beta methyl group, turning it into a carboxylate group; SdmB is a bifunctional enzyme that catalyzes two different activities.
  • As EC it catalyzes an oxidative decarboxylation that results in reduction of the 3beta-hydroxy group at the C-3 carbon to an oxo group.
  • As EC, it reduces the 3-oxo group back to a 3beta-hydroxyl.
  • Since the remaining methyl group at C-4 is in an alpha orientation, it cannot serve as a substrate for a second round of demethylation by this system.
PRIAM enzyme-specific profiles1.1.1.417
KEGG Ligand Database for Enzyme Nomenclature1.1.1.417
IUBMB Enzyme Nomenclature1.1.1.417
MEDLINEFind literature relating to
Rhea expert-curated reactions1.1.1.417

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