ID 2.1.1.131 DE precorrin-3B C(17)-methyltransferase. AN precorrin-3B C17-methyltransferase. AN precorrin-3 methylase. AN precorrin-3 methyltransferase. CA precorrin-3B + S-adenosyl-L-methionine = 3 H(+) + precorrin-4 + CA S-adenosyl-L-homocysteine. CC -!- The enzyme, which participates in the aerobic (late cobalt insertion) CC pathway of adenosylcobalamin biosynthesis, catalyzes a crucial CC reaction where the tetrapyrrole ring contracts as a result of CC methylation of C-17. CC -!- See EC 2.1.1.272 for the corresponding enzyme that participates in CC the anaerobic cobalamin biosynthesis pathway. DR P66878, COBIJ_MYCBO; P9WGB2, COBIJ_MYCTO; P9WGB3, COBIJ_MYCTU; DR P21640, COBJ_SINSX ; //