Nature’s design and use of catalysts based on Co and the macrocyclic corrin ligand: 4 x 10 9 years of coordination chemistry

The Co corrinoids (derivatives of vitamin B12) offer an unrivalled opportunity to assess the separate contributions of the metal, the macrocyclic ring and the protein towards enzymatic activity. We summarise current ideas and evidence on: reasons for the selection of Co, the corrin ring and the Ado ligand; the role of the protein; and the possible function of Co corrinoids in the pre-DNA era.