Enzymic parameters: Measurement of V and Km

A slight modification of the Lineweaver—Burk equation (and other variants) in which the form is retained but the instantaneous velocity is replaced by the negative change in substrate concentration divided by the time and the initial substrate concentration is replaced by the arithmetic average substrate concentration during the time interval, allows this linear reciprocal form to be used with little error even when as much as 50% of the substrate is consumed. This result is in sharp contrast to the prevailing belief that the initial velocities and initial substrate concentrations must be used.