Vitamin B12-derivatives—enzymecofactors and ligands of proteins and nucleic acids

Abstract

B₁₂-cofactors play important roles in the metabolism of microorganisms, animals and humans. Microorganisms are the only natural sources of B₁₂-derivatives, and the latter are “vitamins” for other B₁₂-requiring organisms. Some B₁₂-dependent enzymes catalyze complex isomerisation reactions, such as methylmalonyl-CoA mutase. They need coenzyme B₁₂, an organometallic B₁₂-derivative, to induce enzymatic radical reactions. Another group of widely relevant enzymes catalyzes the transfer of methyl groups, such as methionine synthase, which uses methylcobalamin as cofactor. This tutorial review covers structure and reactivity of B₁₂-derivatives and structural aspects of their interactions with proteins and nucleotides, which are crucial for the efficient catalysis by the important B₁₂-dependent enzymes, and for achieving and regulating uptake and transport of B₁₂-derivatives.