The role of metals in enzyme activity.

Metal ions play important roles in the biological function of many enzymes. The various modes of metal-protein interaction include metal-, ligand-, and enzyme-bridge complexes. Metals can serve as electron donors or acceptors, Lewis acids or structural regulators. Those that participate directly in the catalytic mechanism usually exhibit anomalous physicochemical characteristics reflecting their entatic state. Carboxypeptidase A, liver alcohol dehydrogenase, aspartate transcarbamoylase and alkaline phosphatase exemplify the different roles of metals in metalloenzymes while the nucleotide polymerases point to the essential role of zinc in maintaining normal growth and development.