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An iron-sulfur protein. An oxygen atom from dioxygen is incorporated into the macrocycle at C-20. In the aerobic cobalamin biosynthesis pathway, four enzymes are involved in the conversion of precorrin-3A to precorrin-6A. This enzyme carries out the first of the four steps, yielding precorrin-3B as the product. This is followed by three methylation reactions, which introduce a methyl group at C-17 (CobJ; EC 2.1.1.131), C-11 (CobM; EC 2.1.1.133) and C-1 (CobF; EC 2.1.1.152) of the macrocycle, giving rise to precorrin-4, precorrin-5 and precorrin-6A, respectively. |