Evidence that the insulin receptor‐associated protein kinase acts as a phosphatidylinositol kinase

Insulin receptor preparations from human placenta at various states of purity were shown to catalyze insulin-stimulated phosphate incorporation from [gamma-32P]ATP into endogenous (membrane) and exogenous phosphatidylinositol. Our data suggest that the insulin receptor associated protein (tyrosine) kinase can act as a phosphatidylinositol kinase, and that this mechanism may be of physiological importance in signal transduction of insulin.