Reaction: precorrin-3A + NADH + H+ + O2 = precorrin-3B + NAD+ + H2O
For diagram click here and mechanism here.
Other name(s): precorrin-3X synthase; CobG
Systematic name: precorrin-3A,NADH:oxygen oxidoreductase (20-hydroxylating)
Comments: An iron-sulfur protein. An oxygen atom from dioxygen is incorporated into the macrocycle at C-20. 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 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.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 152787-63-8
References:
1. Debussche, L., Thibaut, D., Cameron, B., Crouzet, J. and Blanche, F. Biosynthesis of the corrin macrocycle of coenzyme B12 in Pseudomonas denitrificans. J. Bacteriol. 175 (1993) 7430-7440. [PMID: 8226690]
2. Scott, A.I., Roessner, C.A., Stolowich, N.J., Spencer, J.B., Min, C. and 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]
3. Warren, M.J., Raux, E., Schubert, H.L. and Escalante-Semerena, J.C. The biosynthesis of adenosylcobalamin (vitamin B12). Nat. Prod. Rep. 19 (2002) 390-412. [PMID: 12195810]