Assay of phosphotyrosyl protein phosphatase using synthetic peptide 1142–1153 of the insulin receptor

• Published in: FEBS letters 1988-09, Vol.237 (1), p.137-140
• Main Authors: King, Martin J., Sale, Graham J.
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolases; Insulin; Kinetics; Liver - enzymology; Peptide Fragments - metabolism; Phosphopeptide; phosphoprotein phosphatase; Phosphoprotein Phosphatases - isolation & purification; Phosphoprotein Phosphatases - metabolism; Phosphorus Radioisotopes; Phosphorylation; Protein phosphatase; Protein phosphorylation; Protein Tyrosine Phosphatases; Rats; Receptor; Receptor, Insulin - metabolism; Tyrosine kinase
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(88)80187-X

Synthetic peptide 1142–1153 of the insulin receptor was phosphorylated on tyrosine by the insulin receptor and found to be a potent substrate for dephosphorylation by rat liver particulate and soluble phosphotyrosyl protein phosphatases. Apparent K m values were $ ̃ 5 μM. V m values (nmol phosphate removed/min per mg protein) were 0.62 (particulate) and 0.2 (soluble). This corresponds to 80% of total activity being membrane-associated, indicating that membrane-bound phosphatases are important receptor phosphatases. The phosphatase activities were distinct from acid and alkaline phosphatase. In conclusion peptide 1142–1153 provides a useful tool for the further study and characterization of phosphotyrosyl protein phosphatases.