Kinetic evidence for activating and non-activating components of autophosphorylation of the insulin receptor protein kinase.
Reduced and carboxamidomethylated-lysozyme (RCAM-lysozyme) is an excellent substrate (Km = 13 microM) and a potent inhibitor of receptor autophosphorylation (Ki = 0.6 microM). By using these properties of RCAM-lysozyme autophosphorylation was resolved into two kinetically and functionally distinct components involving formation of phosphotyrosine on the receptor's beta-subunits: 1. Insulin-stimulated autophosphorylation is independent of autophosphorylation at other sites; activation of insulin receptor-catalyzed substrate phosphorylation is dependent upon this component of autophosphorylation, which is inhibited by RCAM-lysozyme. 2. Autophosphorylation at saturating RCAM-lysozyme concentration is insensitive to insulin and has little effect on substrate phosphorylation. Thus, only insulin-dependent receptor autophosphorylation is responsible for activation of kinase-catalyzed substrate phosphorylation.
D002384:Catalysis; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008745:Methylation; D009113:Muramidase / Q000378:metabolism; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*
D007328:Insulin; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D009113:Muramidase