ID 1.14.13.246 DE 4beta-methylsterol monooxygenase. CA a 3beta-hydroxy-4,4-dimethylsteroid + 2 H(+) + 3 NADH + 3 O2 = a 3beta- CA hydroxy-4alpha-methylsteroid-4beta-carboxylate + 4 H2O + 3 NAD(+). CC -!- Contains a Rieske [2Fe-2S] iron-sulfur cluster. CC -!- This bacterial enzyme (SdmA) participates in the biosynthesis of CC bacterial sterols. CC -!- Together with SdmB it forms an enzyme system that removes one methyl CC group from the C-4 position of 4,4-dimethylated steroid molecules. CC -!- SdmA catalyzes three successive oxidations of the C-4beta methyl CC group, turning it into a carboxylate group; the second enzyme, SdmB, CC is a bifunctional enzyme that catalyzes two different activities. CC -!- As EC 1.1.1.417 it catalyzes an oxidative decarboxylation that CC results in reduction of the 3beta-hydroxy group at the C-3 carbon to CC an oxo group. CC -!- As EC 1.1.1.270 it reduces the 3-oxo group back to a 3beta-hydroxyl. CC -!- Unlike the animal/fungal enzyme EC 1.14.18.9 and the plant enzymes CC EC 1.14.18.10 and EC 1.14.18.11, this enzyme acts preferentially on CC the 4beta-methyl group. CC -!- Since no epimerization of the remaining C-4alpha methyl group occurs, CC the enzyme can only remove one methyl group, leaving a 4alpha- CC monomethylated product. DR Q60A55, SDMA_METCA ; //