The stereoselective recognition of substrates by phosphoinositide kinases
| Autor: | Macphee, C.H., Carter, A.N., Ruiz-Larrea, F., Ward, J.G., Young, R.C., Downes, C.P. |
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| Rok vydání: | 1992 |
| Zdroj: | RIUR. Repositorio Institucional de la Universidad de La Rioja instname RIUR: Repositorio Institucional de la Universidad de La Rioja Universidad de La Rioja (UR) |
| Popis: | 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 M 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. However, neither of the 4-kinases was able to phosphorylate. L-PtdIns and, therefore, these kinases have an absolute requirement for the inositol ring to be linked to the glyceryl backbone of the lipid through the D-1 position. Phosphoinositide 3-kinase, on the other hand, was found to phosphorylate both D- and L-PtdIns. While the 3-kinase phosphorylated exclusively the D-3 position of D-PtdIns, further analyses demonstrated that the same enzyme phosphorylated two sites on L-PtdIns, namely the D-6 and D-5 positions of the inositol ring. Some implications of these findings are discussed. |
| Databáze: | OpenAIRE |
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