Partial purification and characterization of phosphatidylinositol kinase from bovine brain

Purification of Phosphatidylinositol (PI) kinase was attempted from bovine brain. A seven step purification protocol increased the specific activity 100 x but attempts at further purification were unsuccessful. Labeling of the partially purified PI kinase with the ATP analog fluorosulfonylbenzoyl adenosine reproducibly identified three bands on polyacrylamide gel electrophoresis of 76 K, 45 K, and 29 K, one of which likely represents PI kinase. Kinetic studies showed a Km of 17 microM for ATP, 0.02 mg/ml for PI and a Vm of 1830 pmol/min/mg protein for ATP and 820 pmol/min/mg protein for PI.