The phosphatidylinositol kinase of rat brain

1. The presence of a phosphatidylinositol kinase in homogenates of adult rat brain was shown by using labelled ATP or labelled phosphatidylinositol. 2. The kinase was activated by Mg(2+) or Mn(2+) and inhibited by Ca(2+), Cu(2+), K(+), Na(+) and F(-). 3. The detergents sodium deoxycholate, Cutscum and Triton X-100 markedly stimulated the reaction; sodium taurocholate, Tween-20 and cetyltrimethyl-ammonium bromide were less effective. 4. The activity of the enzyme was dependent on SH groups. 5. The subcellular distribution of the kinase in brain resembled that of Na(+)-plus-K(+)-stimulated adenosine triphosphatase and 5'-nucleotidase.