Theory 11/Seconds to Minutes/Enzyme kinetics
Turnover Is Encounter Against Chemistry
The claim
Enzyme turnover rate is set by the ratio of substrate encounter time to catalytic time, so a fast catalyst in a dilute solution is limited by diffusion rather than by chemistry.
01Mechanism
The substrate must arrive before the chemistry can proceed; whichever step is slower sets the rate, and the ratio determines which.
02Prediction
Rate should track the ratio across concentrations.
03Refutation
Rate tracking kcat alone would remove encounter.