The coordination chemistry of vanadium as related to its biological functions

The binding of vanadium to protein side-chains such as provided by tyrosina te, serinate, aspartate, glutamate, cysteinate, methionine and histidine is modelled by complexes with ligand sets containing phenolate, alkoxide, car boxylate, thiolate, thioether and enamine functions. The complexes mimic po ssible intermediates and structural motifs of the coordination environment of vanadium in vanadium-nitrogenase, vanadate-dependent haloperoxidases, th e interaction with phosphorylation enzymes, and the redox-interaction with cysteinyl residues. The solid state investigations are supplemented by solu tion studies on vanadate-dipeptide and vanadate-adenosine systems, based on combined V-51-NMR and potentiometric measurements. Model reactions for the function of haloperoxidases and vanadium-nitrogenase (including the alkyne -reductase and isonitrile-reductase/ligase activities) are described, and t he impact of these investigations for corresponding in vitro applications i s dealt with. The relevance of catecholatovanadium complexes for the accumu lation of vanadium by ascidians is also addressed. (C) 1999 Elsevier Scienc e S.A. All rights reserved.