COMPUTERIZED ANALYSIS OF COVALENT INHIBITION-KINETICS FOR IDENTIFICATION OF HEART-MUSCLE CHOLINESTERASE AND BRAIN CARBOXYLESTERASE ISOENZYMES - DESIGN OF DIFFERENTIAL INHIBITION ASSAYS

The kinetics of time- and concentration-dependent covalent organophosp horus inhibition of carboxylesterase isoenzymes (EC 3.1.1.1) and choli nesterase isoenzymes (EC 3.1.1.7 and EC 3.1.1.8) were investigated usi ng a wide range of organophosphate inhibitor concentrations (10(-10)- 10(-3) mol/l) and different inhibition times. Computerized analysis of inhibition curves by weighted nonlinear least-squares curve fitting w as compared to graphic analysis by iterative elimination of exponentia l functions. Possible experimental errors due to inhibitor saturation kinetics and enzymatic organophosphate hydrolysis were thoroughly inve stigated. In mammalian heart muscle, three different cholinesterase is oenzymes were identified. High sensitivity and specificity of the clas sic differential inhibition test for carboxylesterase activity of hen brain neuropathy target esterase (NTE) could be confirmed independentl y with both methods of inhibition curve analysis.