KINLSQ - A PROGRAM FOR FITTING KINETICS DATA WITH NUMERICALLY INTEGRATED RATE-EQUATIONS AND ITS APPLICATION TO THE ANALYSIS OF SLOW, TIGHT-BINDING INHIBITION DATA

Kinlsq, a Matlab-based computer program for the least-squares fitting of parameters to kinetics data described by numerically integrated rat e equations, is described, and three applications to the analysis of e nzyme kinetics data are given. The first application was to the analys is of a simple bimolecular enzyme plus inhibitor binding curve. The ki nlsq fit to these data was essentially identical to that obtained with the corresponding analytically integrated rate equation, validating k inlsq. The second application was to the fit of a numerically integrat ed Michaelis-Menten model to the progress curve for dipeptidyl peptida se IV-catalyzed hydrolysis of Ala-Pro-p-nitroanilide as a demonstratio n of the analysis of steady-state enzyme kinetics data. The results ob tained with kinlsq were compared with the results obtained by fitting this time course with the integrated Michaelis-Menten equation, and wi th the results obtained by fitting the (S,dP/dt) transform of the data with the Michaelis-Menten equation. The third application was to the analysis of the inhibition of chymotrypsin by the slow, tight-binding inhibitor MeOSuc-Ala-Ala-Pro-boroPhe, data not readily amenable to oth er methods of analysis. These applications demonstrate how kinlsq can be used to fit rate constants, equilibrium constants, steady-state con stants, and the stoichiometric relationships between components. (C) 1 994 Academic Press, Inc.