Turnover and Catalytic cycle frequency Determination based on Molar mass-dependent Model equations

Abstract

There were conflicting definitions and misrepresentations of turnover frequency (TOF), catalytic cycle frequency (CCF), and catalytic first-order rate constant (kcat) in the literature. Based on the Benfield and Lineweaver-Burk methods, data were generated. The results showed that the CCF for the forward (3.63 exp. (+7)/s) and reverse (1.196 exp. (+9)/s) and the TOF (8.294 exp. (−4)/s) were respectively the highest and lowest for the highest concentration [E0] of the enzyme. The number of fragments per molecule of an enzyme was = f([ET]), where [ET] was in molar units and it was ≫ [ST] (in molar units), and where [ST] ≫ [ET], it was = f([ST]. In conclusion, TOF and CCF were different, and in particular, the former was not the same as kcat, while the latter was a constant. TOF and CCF vary. Strictly speaking, TOF was = f(M3). This can be verified with sucrase in a future study.