ENZYME entry: EC 1.14.13.246

Accepted Name

4beta-methylsterol monooxygenase

Reaction catalysed

a 3beta-hydroxy-4,4-dimethylsteroid + 3 NADH + 3 O2 + 2 H(+) = a 3beta-hydroxy-4alpha-methylsteroid-4beta-carboxylate + 3 NAD(+) + 4 H2O

Comment(s)

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 1.1.1.417 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 1.1.1.270 it reduces the 3-oxo group back to a 3beta-hydroxyl.
Unlike the animal/fungal enzyme EC 1.14.18.9 and the plant enzymes EC 1.14.18.10 and EC 1.14.18.11, 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.

Cross-references

BRENDA

EC2PDB

ExplorEnz

KEGG Ligand Database for Enzyme Nomenclature

IUBMB Enzyme Nomenclature

MEDLINE

MetaCyc

Rhea expert-curated reactions

UniProtKB/Swiss-Prot

Q60A55, SDMA_METCA

All UniProtKB/Swiss-Prot entries referenced in this entry, with possibility to download in different formats, align etc.

All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 1.14.13.-
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 1.14.-.-
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