Understanding initial velocity after the derivatives of progress curves

A simple approach to facilitate, in practical terms, the understanding of the concept of initial velocity is proposed. After monitoring colorimetrically p ‐nitrophenol appearance due to alkaline phosphatase hydrolysis of p ‐nitrophenylphosphate, in an experimental protocol that takes little more than 10 min, derivatives of progress curves are obtained. These plots of velocity vs. time result a valuable educational tool to evaluate effects of inaccurate estimates of initial velocity on the calculation of the K M and V max parameters.