ISU, Biochemistry, Normal, IL 61790
Orthovanadate (VO43-) is similar in shape, size and charge to phosphate (PO43-) and has been shown to enhance the action of insulin. This activity is reported to be through signaling pathways that involve the inhibition of phosphotyrosine-phosphatase (PTP) as well as interaction between two non-insulin receptor tyrosine kinases. In this study, I tested for enzyme inhibition by several unique vanadium complexes on three different phosphatases (acid, alkaline and phosphotyrosine phosphatase) using the substrate p-nitrophenyl phosphate (p-NPP). The levels of inhibition were determined by measuring the absorbance of the product by electronic absorbance (UV/vis) spectroscopy at 405nm. Orthovanadate is known to inhibit the removal of the phosphate group from p-NPP by competitively binding to the active site of acid, alkaline or phosphotyrosine phosphatase. However, my results show that our vanadium complex is an uncompetitive inhibitor of alkaline phosphatase and phosphotyrosine-phosphatase, and a noncompetitive inhibitor of acid phosphatase. Under our conditions, our compound proved to be a more effective phosphatase inhibitor than the known inhibitor Na3VO4, whereas other new vanadium compounds that were tested using acid phosphatase were less effective as inhibitors. These data confirm the inhibitory nature of our vanadium complexes on selected enzymes, which may help elucidate the mechanism whereby they act as insulin enhancing agents.
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