Biochemical catalysis involving coenzyme B-12: a rational stepwise mechanistic interpretation of vicinal interchange rearrangements.

Abstract

A mechanism is proposed for the catalytic action of coenzyme B-12 which is consistent with current knowledge of organometallic reactions and with the experimental data now available from biochemical studies. A key feature of the proposal is an electrocyclic cleavage of the coenzyme that reduces cobalt and also leads to a 1,19-seco-corrin. The seco-corrin serves as a tridentate ligand about Co(I). This arrangement permits the metal to take part in the kinds of organometallic reactions that are ideal for coenzyme B-12 catalysis, including oxidative addition and its reverse, reductive elimination. It is further proposed that the rearrangement steps involve cobaltcarbene complexes.

Bioorganic Chemistry

“…Corey proposed in 1977 an interesting and different mechanism, consistent with current knowledge of organometallic reactions (530). Corey proposed in 1977 an interesting and different mechanism, consistent with current knowledge of organometallic reactions (530).…”

Bioorganic Chemistry

“…However, convincing direct evidence for the intermediacy of carbon radicals in natural coenzyme B12 rearrangements is still lacking and for this reason E. J. Corey proposed in 1977 an interesting and different mechanism, consistent with current knowledge of organometallic reactions (268). A key feature of the proposal is an electrocyclic opening of the corrin ring of the coenzyme, cleaving the unique direct chemical bond that joins ring A and D (see Fig.…”

Role of peripheral side chains of vitamin B12 coenzymes in the reaction catalyzed by dioldehydrase

“…investigators (Schrauzer, 1971;Corey et al, 1977). An early event in the proposed mechanism is the homolytic cleavage of the C-Co bond of the coenzymes.…”