title: Protein tyrosine phosphorylation activates rat splenic type II phosphatidylinositol 4-kinase in vitro.
abstract: Regulation of phosphatidylinositol 4-kinase (PtdIns 4-kinase) by protein tyrosine phosphorylation has been indirect and the effects of phosphorylation are debatable. Rat splenic type II PtdIns 4-kinase was phosphorylated in vitro with protein tyrosine kinases from Con A stimulated splenic lymphocytes. Stoichiometric analysis showed one mole of phosphate was incorporated per mole of PtdIns 4-kinase. Tyrosine phosphorylation increased the enzyme activity by 3-fold. Kinetic analysis showed a reduction in Km for PtdIns and an increase in Vmax. Dephosphorylation with protein phosphotyrosine phosphatase abolished the activation of PtdIns 4-kinase while protein phosphatase 2A had no effect. Protein tyrosine phosphorylation and activation of PtdIns 4-kinase appear to be tissue specific.
authors.affiliation: Biotechnology Centre, Indian Institute of Technology, Bombay Powai, Mumbai.
authors.forename: A Z
authors.initials: AZ
authors.lastname: Fernandis
authors.forename: G
authors.initials: G
authors.lastname: Subrahmanyam
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism*; D000818:Animals; D003208:Concanavalin A / Q000494:pharmacology; D004789:Enzyme Activation; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D013154:Spleen / Q000166:cytology / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D003208:Concanavalin A; D014443:Tyrosine; D019870:1-Phosphatidylinositol 4-Kinase; D011505:Protein-Tyrosine Kinases