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ENZYME entry: EC

Accepted Name
4beta-methylsterol monooxygenase
Reaction catalysed
a 3beta-hydroxy-4,4-dimethylsteroid + 2 H(+) + 3 NADH + 3 O2 <=> a 3beta-hydroxy-4alpha-methylsteroid-4beta-carboxylate + 4 H2O + 3 NAD(+)
  • Contains a Rieske [2Fe-2S] iron-sulfur cluster.
  • This bacterial enzyme (SdmA) participates in the biosynthesis of bacterial sterols.
  • Together with SdmB 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; the second enzyme, 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.
  • Unlike the animal/fungal enzyme EC and the plant enzymes EC and EC, this enzyme acts preferentially on the 4beta-methyl group.
  • Since no epimerization of the remaining C-4alpha methyl group occurs, the enzyme can only remove one methyl group, leaving a 4alpha- monomethylated product.
PRIAM enzyme-specific profiles1.14.13.246
KEGG Ligand Database for Enzyme Nomenclature1.14.13.246
IUBMB Enzyme Nomenclature1.14.13.246
MEDLINEFind literature relating to
Rhea expert-curated reactions1.14.13.246

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