title: Identification, purification, and partial characterization of plasma protein kinases.
abstract: Two isomeric forms of protein kinases, FI and FII, were isolated from human plasma. These two isomeric enzymes were isolated to apparent homogeneity on NaDodSO4-PAGE by using (NH4)2SO4 fractionation, DEAE-cellulose, hydroxylapatite, Affi-Gel blue, and high-pressure liquid column chromatography. Polyclonal antibodies were obtained from immunized rabbits and both enzymes cross-reacted with each other. Furthermore, immunoaffinity-purified anti-FI and anti-FII antibodies inhibited the enzyme activity of both FI and FII. These enzymes are cyclic nucleotides, Ca2+, calmodulin and phosphatidylserine-independent enzymes which can phosphorylate exogenously added histone, casein, protamine, phosvitin, and platelet surface proteins. The phosphorylated proteins of intact platelets by these enzymes in the presence of exogenously added [gamma-32P]ATP ranged in apparent molecular weights from 13.5K to 200K, as estimated by their mobility during NaDodSO4-PAGE. Trypsin removed the label from the platelet surface phosphoproteins without affecting the intracellularly located phosphoproteins labeled endogenously by 32PO4-prelabeling of intact platelets. These observations raise the possibility that these enzymes could play a role in modulating the properties of platelets through phosphorylation of the platelet surface proteins.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001345:Autoradiography; D001792:Blood Platelets / Q000201:enzymology; D002848:Chromatography, DEAE-Cellulose; D002851:Chromatography, High Pressure Liquid; D003101:Collodion; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007120:Immunochemistry; D007074:Immunoglobulin G / Q000302:isolation & purification; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood* / Q000145:classification / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D007074:Immunoglobulin G; D003101:Collodion; D011494:Protein Kinases