ID 1.14.13.246 DE 4-beta-methylsterol monooxygenase. CA A 3-beta-hydroxy-4,4-dimethylsteroid + 3 NADH + 3 O(2) = a 3-beta- CA hydroxy-4-beta-carboxy-4-alpha-methylsteroid + 3 NAD(+) + 4 H(2)O. 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-4-beta 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 3-beta-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 3-beta-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 4-beta-methyl group. CC -!- Since no epimerization of the remaining C-4-alpha methyl group CC occurs, the enzyme can only remove one methyl group, leaving a CC 4-alpha-monomethylated product. //