The Inactivation Mechanism of Low Molecular Weight Phosphotyrosine-Protein Phosphatase by H2O2

Abstract

Low molecular weight phosphotyrosine-protein phosphatase (LMW-PTP) shares no general sequence homology with other PTPs, although it has an active site sequence motif CXXXXXR and a reaction mechanism identical to those of all PTPs. The main function of this enzyme is the down-regulation of platelet-derived growth factor and insulin receptors. Both human LMW-PTP isoenzymes are inactivated by H 2 O 2 . The enzymes are protected from inactivation by P i , a competitive inhibitor, suggesting that the H 2 O 2 react…