Sensitivity of protein tyrosine phosphatase activity to the redox environment, cytochrome C, and microperoxidase.
Protein tyrosine phosphatase activity depends on a catalytic thiolate group on an acidic cysteine residue that is sensitive to reactive oxygen species. Representative of this family of enzymes is protein tyrosine phosphatase 1B (PTP1B), a major target for type 2 diabetes therapy. PTP1B is sensitive to hydrogen peroxide (H2O2) in vitro and in cells. It is also sensitive to glutathionylation by glutathione disulfide (GSSG). The sensitivity of PTP1B to the redox state of its environment was partially characterized in vitro by examination of phosphatase activity in the presence of various concentrations of glutathione (GSH) and GSSG. Enzyme sensitivity to glutathionylation was dependent on the amount of available thiol groups and increased as GSH concentration was increased. The half-inhibitory concentration for H2O2 was much less than that of GSSG in the presence of low concentrations of GSH, indicating that reaction with H2O2 is much more likely than is glutathionylation by GSSG. PTP1B and a related oxidant-sensitive phosphatase, PTEN, were also sensitive to the lipid peroxidation by-product 4-hydroxynonenal. Furthermore, PTP1B was inhibited by cytochrome c and microperoxidase. Taken together, these data suggest that not only H2O2, but also a variety of redox-active metabolites and hemes can oxidatively inactivate PTPs with potentially profound implications for signal transduction.
Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
Scott J
SJ
Salsman
Kenneth
K
Hensley
Robert A
RA
Floyd
D000478:Alkylation; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019803:Glutathione Disulfide / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D010084:Oxidation-Reduction; D051059:PTEN Phosphohydrolase; D010544:Peroxidases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D004791:Enzyme Inhibitors; D013438:Sulfhydryl Compounds; D025521:Tumor Suppressor Proteins; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021799:microperoxidase; D010744:Phosphoric Monoester Hydrolases; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D003545:Cysteine; D019803:Glutathione Disulfide