The stereoselective recognition of substrates by phosphoinositide kinases : studies using synthetic stereoisomers of dipalmitoyl phosphatidylinositol

Soluble phosphatidylinositol (PtdIns) 4- and 3-kinase activities were partially purified and characterized from human placental extracts. The placental PtdIns 4-kinase (type 3) has a K m for ATP of 460 μM and is kinetically different to a partially purified human erythrocyte, membrane-bound, PtdIns 4-kinase (type 2). These three inositol lipid kinases were then used to compare their substrate specificities against the four synthetic stereoisomers of dipalmitoyl PtdIns. Only the placental 4-kinase was influenced by the chirality of the glycerol moiety of PtdIns