Cooperation of metals with electroactive ligands of biochemical relevance: Beyond metalloporphyrins
In addition to the widely studied biometal complexes of tetrapyrrole ligands such as hemes (Fe), cobalamins (Co), and factor F430 (Ni), there are other, more recently established systems in which transition metals and redox-active cofactors such as pterins, flavins, quinones, or phenoxyl radicals cooperate in electron transfer and substrate activation. The cases of the molybdenum or tungsten containing oxotransferases involving pyranopterin as essential ligand and the copper-dependent quinoproteins such as amine oxidases will be discussed. The structural and functional description of these systems will be complemented by results from model studies.