Purification of a Phosphatidylinositol 4‐Phosphate Kinase from Bovine Brain Membranes

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Abstract
A phosphatidylinositol 4‐phosphate (PIP) kinase (EC 2.7.1.68) was purified from bovine brain membranes in a six‐step procedure involving solubilization of the enzyme with 170 mM NaCl followed by chromatography on diethylaminoethyl‐cellulose, phosphocellulose, Ultrogel AcA44, hydroxylapatite, and ATP‐agarose. The enzyme preparation was nearly homogeneous and was purified 5,600‐fold with a final specific activity of 85 nmol/min/mg of protein and a yield of 20%. Its molecular mass was 110 kilodaltons, as estimated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. The enzyme was specific for PIP; phosphorylation of phosphatidylinositol and diacylglycerol was not observed.