In the aerobic (late cobalt insertion) cobalamin biosythesis pathway, four enzymes are involved in the conversion of precorrin-3A to precorrin-6A. The first of the four steps is carried out by EC
1.14.13.83, precorrin-3B synthase (CobG), 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. See EC
2.1.1.271, cobalt-precorrin-4 methyltransferase, for the C11-methyltransferase enzyme that participates in the anaerobic cobalamin biosynthesis pathway.
