ID 1.14.18.11 DE plant 4alpha-monomethylsterol monooxygenase. CA 24-methylidenelophenol + 6 Fe(II)-[cytochrome b5] + 5 H(+) + 3 O2 = CA 4alpha-carboxy-ergosta-7,24(24(1))-dien-3beta-ol + 6 Fe(III)-[cytochrome CA b5] + 4 H2O. CC -!- This plant enzyme catalyzes a step in the biosynthesis of sterols. CC -!- It acts on the methyl group of the 4alpha-methylated intermediates CC 24-ethylidenelophenol and 24-methylidenelophenol and catalyzes three CC successive oxidations, turning it into a carboxyl group. CC -!- The carboxylate is subsequently removed by EC 1.1.1.418. CC -!- Unlike the fungal/animal enzyme EC 1.14.18.9, this enzyme is not able CC to act on 4,4-dimethylated substrates. CC -!- That activity, which occurs earlier in the pathway, is performed in CC plants by a second enzyme, EC 1.14.18.10. DR F4JLZ6, SMO13_ARATH; Q9ZW22, SMO21_ARATH; Q8VWZ8, SMO22_ARATH; //