Application of the Van Slyke-Cullen irreversible mechanism in the analysis of enzymatic progress curves

For enzymatic progress curves conforming to the Michaelis-Menten mechanism E+Sright harpoon over left harpoonES-->E+P, the minimal fitting model cast as a system of numerically integrated differential equations is the simplified, irreversible Van Slyke-Cullen mechanism E+S-->ES-->E+P. The best-fit value of the bimolecular association rate constant is identical to the specificity constant kcat/KM. An illustrative example involves a fluorogenic continuous assay of the HIV protease, analyzed by the differential-equation oriented software package DYNAFIT [P. Kuzmic, Anal. Biochem. 237 (1996) 260].