Assay of phosphotyrosyl protein phosphatase using synthetic peptide 1142-1153 of the insulin receptor.
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 Km values were approximately 5 microM. Vm 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.
King
M J
MJ
Department of Biochemistry, School of Biochemical and Physiological Sciences, University of Southampton, England.
Sale
G J
GJ
D000818:Animals; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D010446:Peptide Fragments / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*
D010446:Peptide Fragments; D010761:Phosphorus Radioisotopes; D011972:Receptor, Insulin; D010749:Phosphoprotein Phosphatases; D017027:Protein Tyrosine Phosphatases