Specific enhancement of the cardiac myofibrillar ATPase by bound creatine kinase.

摘要: The kinetic influence of bound creatine kinase (CK) on the Ca(2+)-activated myosin ATPase was evaluated. rates were measured from 0.8 microM to 3.2 mM MgATP. Under control conditions, apparent KmATP 79.9 +/- 13.3 microM. In contrast, addition 12.2 phosphocreatine (PCr) decreased a value 13.6 1.4 To determine if this reduction merely result an ATP maintenance system, regenerated using either phosphoenolpyruvate and pyruvate (PEP-PK), or PCr soluble bovine cardiac CK. Data obtained with PEP + PK indicated 65.5 7.3 study effects exogenous CK, endogenous CK irreversibly inhibited 1 iodoacetamide. kinetics then examined by adding incubation medium. these 56.4 0.86 Therefore, two regeneration systems could not duplicate altered inhibition MgADP. MgADP determined be non-competitive, Ki 5.0 0.1 mM. These data suggest that observed reflect proximity enzymes in myofibrillar bundle, thus emphasizing importance for localized MgATP utilized ATPase.