[41] Use of vanadate as protein-phosphotyrosine phosphatase inhibitor

This chapter discusses the use of vanadate as protein-phosphotyrosine phosphatase inhibitor. Vanadium ions have found widespread use as an inhibitor of protein-phosphotyrosine phosphatases. Some form of vanadium ion is added to preserve the phosphotyrosine content of cells, cell lysates, and tyrosine kinase assays. Protein-phosphotyrosine phosphatase (PPTPase) activity is found in most mammalian and avian cells and tissues as well as in bacterial and yeast cultures. This uncertainty in substrate suitability may influence the effectiveness of inhibitors. The multiple phosphotyrosine phosphatases may be more or less sensitive to the same inhibitor. The protein-phosphotyrosine phosphatase activities sensitive to inhibition by zinc chloride and sodium orthovanadate are conveniently separable from the phosphoseryl and phosphothreonyl phosphatase activities inhibited by EDTA and fluoride.