Hepatic protein tyrosine phosphatases in the rat

P. A. Gruppuso, J. M. Boylan, B. L. Smiley, R. J. Fallon, D. L. Brautigan

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18 Scopus citations


Regulation of cell growth and metabolism by protein tyrosine phosphorylation involves dephosphorylation via the action of protein tyrosine phosphatases (PTPases). We have characterized the membrane PTPases in rat liver, monitoring their activity by measuring the dephosphorylation of P-Tyr-reduced, carboxyamidomethylated and maleylated lysozyme (P-Tyr-RCML) and P-Tyr-myelin basic protein (P-Tyr-M BP). Separation of membrane PTPases by poly (L-lysine) chromatography yielded three peaks of PTPase, termed I, II and III. PTPases I and II were most active with P-Tyr-RCML, whereas PTPase III showed greater activity with P-Tyr-MBP than with P-Tyr-RCML (ratio of activities 4: 1). Separation of membrane proteins by gel-filtration chromatography yielded two peaks of activity. Based on substrate specificity, sensitivity to inhibitors and requirement for thiol-containing compounds, the activity peak with an M(r) of ~400000 corresponded to PTPase III, whereas that with an M(r) of approx. 40000 contained PTPases I and II. All three PTPases dephosphorylated epidermal growth factor receptors and insulin receptors, but only PTPases I and II were active with P-Tyr-asialoglycoprotein receptors. Although none of the above characteristics distinguished between PTPases I and II, only PTPase I reacted in a Western immunoblotting procedure with anti-peptide antibodies directed towards human placental PTPase. We conclude that the membrane fraction from rat liver contains at least three distinct PTPases.

Original languageEnglish (US)
Pages (from-to)361-367
Number of pages7
JournalBiochemical Journal
Issue number2
StatePublished - 1991

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Gruppuso, P. A., Boylan, J. M., Smiley, B. L., Fallon, R. J., & Brautigan, D. L. (1991). Hepatic protein tyrosine phosphatases in the rat. Biochemical Journal, 274(2), 361-367. https://doi.org/10.1042/bj2740361