   3.1.3.67 | phosphatidylinositol 4,5-biphosphate |
Enhances PTEN phosphatase activity by inducing conformational change by binding to the PTEN N-terminal domain. Binding constants are in accord with enzyme kinetic measurements showing that phosphatidylinositol 4,5-bisphosphate enhances phosphatidylinositol 3,4,5-triphosphate hydrolysis more effectively than phosphatidylserine, and the binding constant of phosphatidylinositol 4,5-biphosphate of 8.14 microM is in general agreement with the phosphatidylinositol 4,5-bisphosphate concentration requires to activate the PTEN phosphatase. The magnitude of this binding constant indicates that PTEN-phosphatidylinositol 4,5-bisphosphate interactions are physiologically relevant since the effective cellular concentration of phosphatidylinositol 4,5-bisphosphate is thought to be 10 microM, and local phosphatidylinositol 4,5-bisphosphate concentrations are likely to reach even higher levels. Increasing the phosphatidylserine concentration to 25 mol results in stronger binding, but even for these higher surface charge densities, binding constant is still lower than the corresponding values for the phosphatidylcholine/phosphatidylinositol 4,5-bisphosphate vesicle system. |
690927 |
