Phosphotyrosyl-protein phosphatase of TCRC-2 cells

Swarup, G. ; Speeg, K. V. ; Cohen, S. ; Garbers, D. L. (1982) Phosphotyrosyl-protein phosphatase of TCRC-2 cells Journal of Biological Chemistry, 257 (13). pp. 7298-7301. ISSN 0021-9258

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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.

Item Type:Article
Source:Copyright of this article belongs to The American Society for Biochemistry and Molecular Biology.
ID Code:55934
Deposited On:19 Aug 2011 07:54
Last Modified:19 Aug 2011 07:54

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