Phosphotyrosyl-protein phosphatase of TCRC-2 cells.
Homogenization of TCRC-2 cells yielded a phosphotyrosyl-protein phosphatase with a specific activity approximately 10-=fold higher in particulate than in soluble fractions. Over 90% of the phosphotyrosyl-protein phosphatase associated with the particles was solubilized with 1.0% Nonidet P-40. Chromatography of the detergent-solubilized particulate fraction on either wheat germ lectin-Sepharose or histone-Sepharose columns separated two major components of phosphatase activity. One peak (eluted with 200 mM NaCl from histone-Sepharose or with N-acetylglucosamine from the lectin column) contained both phosphotyrosyl- and phosphoseryl-protein phosphatase as well as p-nitrophenyl phosphatase activities. The other peak (eluted with 1.0 M NaCl from histone-Sepharose or not bound to the lectin column) contained essentially only phosphoseryl-protein phosphatase activity. Various agents (EDTA, p-nitrophenyl phosphate, fluoride) showed considerable differences in their ability to inhibit the two phosphatase fractions; of these, the most potent and selective inhibitor was orthovanadate. At micromolar concentrations, vanadate inhibited the fraction containing phosphotyrosyl-protein phosphatase and failed to inhibit the fraction containing only phosphoseryl-protein phosphatase activity. These data show that the particulate forms of phosphotyrosyl-protein phosphatase and p-nitrophenyl phosphatase represent the activities of very similar or identical proteins.
D002846:Chromatography, Affinity; D006367:HeLa Cells / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
D014639:Vanadium; D014638:Vanadates; D010749:Phosphoprotein Phosphatases