Protein tyrosine phosphatase 1B: A target for vanadium's insulin-enhancing behavior

My dissertation involves an investigation of the role vanadium-containing compounds play in increasing insulin's efficacy in controlling blood glucose levels. It is well known that certain vanadium-containing compounds function as positive regulators of insulin activity, but the mechanism by which insulin-enhancement occurs has not been fully elucidated. Protein tyrosine phosphatase 1B (PTP 1B), an enzyme shown to play an important role in insulin regulation, negates insulin activity by removing phosphate groups (PO43-) from insulin receptor and other post-receptor substrates involved in the insulin signaling pathway. A plausible explanation is that vanadium-containing compounds inhibit PTP 1B activity, which allows required phosphorylation reactions to proceed normally. My dissertation research is designed to test this hypothesis. A series of specifically modified vanadium-containing compounds have been synthesized, and these compounds strongly inhibit (low micromolar range) a general alkaline phosphatase obtained from calf intestine. A correlation between positive charge on the vanadyl group and inhibition potency of the compound was found. However, a new mode of inhibition against PTP 1B was observed. The kinetic results suggest that the compounds are binding to more than one site on PTP 1B. Additionally, assays using a more physiologically relevant substrate, i.e., a peptide that binds more tightly to PTP 1B, have been completed, where the competitive inhibition results suggest a more positive V=O center improves inhibition potency with one exception. Ultimately, an array of structural and spectroscopic techniques has been utilized to gain a more thorough understanding of the mode of enzyme inhibition. These studies have provided fundamental new knowledge about the biochemistry of phosphatase inhibition and vanadium's insulin-enhancing behavior.