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ENZYME entry: EC

Accepted Name
4-beta-methylsterol monooxygenase.
Reaction catalysed
A 3-beta-hydroxy-4,4-dimethylsteroid + 3 NADH + 3 O(2) <=> a 3-beta-hydroxy-4-beta-carboxy-4-alpha-methylsteroid + 3 NAD(+) + 4 H(2)O
  • 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-4-beta 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 3-beta-hydroxy group at the C-3 carbon to an oxo group.
  • As EC it reduces the 3-oxo group back to a 3-beta-hydroxyl.
  • Unlike the animal/fungal enzyme EC and the plant enzymes EC and EC, this enzyme acts preferentially on the 4-beta-methyl group.
  • Since no epimerization of the remaining C-4-alpha methyl group occurs, the enzyme can only remove one methyl group, leaving a 4-alpha-monomethylated product.
PRIAM enzyme-specific profiles1.14.13.246
KEGG Ligand Database for Enzyme Nomenclature1.14.13.246
IUBMB Enzyme Nomenclature1.14.13.246
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