Reaction: S-adenosyl-L-methionine + precorrin-3B = S-adenosyl-L-homocysteine + precorrin-4
For diagram click here and mechanism (here).
Other name(s): precorrin-3 methyltransferase; CobJ
Systematic name: S-adenosyl-L-methionine:precorrin-3B C17-methyltransferase
Comments: The enzyme, which participates in the aerobic (late cobalt insertion) pathway of adenosylcobalamin biosynthesis, catalyses a crucial reaction where the tetrapyrrole ring contracts as a result of methylation of C-17. See EC 184.108.40.2062, cobalt-factor III methyltransferase, for the corresponding enzyme that participates in the anaerobic cobalamin biosynthesis pathway.
Comments: In the aerobic 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 220.127.116.11, 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 18.104.22.168), C-11 (CobM; EC 22.214.171.124) and C-1 (CobF; EC 126.96.36.199) of the macrocycle, giving rise to precorrin-4, precorrin-5 and precorrin-6A, respectively.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 152787-64-9
1. Scott, A.I., Roessner, C.A., Stolowich, N.J., Spencer, J.B., Min, C., Ozaki, S.I. Biosynthesis of vitamin B12. Discovery of the enzymes for oxidative ring contraction and insertion of the fourth methyl group. FEBS Lett. 331 (1993) 105-108. [PMID: 8405386]
2. Debussche, L., Thibaut, D., Cameron, B., Crouzet, J., Blanche, F.J. Biosynthesis of the corrin macrocycle of coenzyme B12 in Pseudomonas denitrificans. J. Bacteriol. 175 (1993) 7430-7440. [PMID: 8226690]