Partial-purification and Characterization of Phosphotyrosyl-protein Phosphatase(s) From Human-erythrocyte Cytosol

Phosphotyrosyl-protein phosphatase activity of human erythrocyte cytosol can be resolved into two fractions by DEAE-cellulose chromatography followed by P-cellulose chromatography. Both 32P-Tyr-phosphatases are able to dephosphorylate 32P-Tyr of poly (Glu-Tyr) 4:1 but not angiotensin II and synthetic peptide Asp-Ala-Glu-Tyr-Ala-Ala-Arg-Arg-Gly, previously phosphorylated on tyrosine residues by rat spleen tyrosine-protein kinase. Both 32P-Tyr-phosphatase activities distinctly differ from either 32P-Ser-casein phosphatase activity or "acid" and "alkaline" p-nitrophenylphosphatase activities with regard to catalytic and physico-chemical properties such as substrate specificity, chromatographic behaviour, response to various effectors.