Determination of the maximum velocity and Michaelis constant of enzymes by a fixed-point method which avoids the necessity to measure initial rates.

Measuring the initial velocity is difficult in some enzyme assays where a significant fraction of the substrate is consumed. Here a solution to this problem is proposed; the time to produce a fixed amount of reaction product is measured. This time is inversely proportional to the initial velocity, and is related to the maximum velocity and Michaelis constant by a simple equation and linear plot. The method is illustrated using the reaction catalysed by pyruvate kinase.