Abstract
A background perspective on vanadium biochemistry relevant to the conference is presented. Vanadate is an extremely effective inhibitor of Na,K-ATPase and many other phosphohydrolase enzymes. Vanadate's ability to mimic phosphate in a transition state configuration underlies its potent inhibition. V-containing haloperoxidases utilize vanadate as a prosthetic group in their active sites. These enzymes catalyze hydrogen peroxide oxidation of a halide ion and subsequent addition of the product to an organic substrate, but the oxidation number of vanadium does not change during the catalytic cycle. Vanadate's role is to coordinate peroxide and facilitate halide ion oxidation, probably by O-atom transfer. Recent evidence suggests that the binding site compositions of both types of enzyme are similar. Apart from enzymes, vanadium is spectacularly accumulated in tunicates, but with as yet unknown function. Two models that accomplish this accumulation have been postulated and are discussed. One utilizes a biogenic reductant and metal ion complexing agent such as tunichrome; the other involves direct participation of enzymes.