Metalloenzymes

Metalloenzymes are a large class of enzymes that utilise a metal cation as a cofactor in the enzyme active site. The enzymes encourage a variety of reactions, such as hydrolytic processes and oxidations/reductions. Examples include vitamin-B-dependent enzymes that transfer methyl groups between molecules, nitrogenases that fix nitrogen from the atmosphere, proteases that break down amide bonds, phosphodiesterases that break down phosphate ester bonds, superoxide dismutases that eliminate superoxide anion, hydrogenases that encourage the uptake of molecular hydrogen, and ribozymes that go through self-cleaving reactions. 5–9 Each of the aforementioned systems has a unique function for the metal cation, which performs as a Lewis acid or a redox partner and promotes the catalysed reaction by improving substrate binding and increasing the ground state energies of reaction partners.