The specific velocity plot. A graphical method for determining inhibition parameters for both linear and hyperbolic enzyme inhibitors.

Abstract

A new method is described for plotting kinetic results for inhibited enzymatic reactions. The plot is particularly designed for the analysis of hyperbolic, mixed-type inhibitors, but can be applied to any other linear system. The method consists of plotting experimental data in a normalized way, as v0/vi versus the specific velocity sigma/(1 + sigma), where v0/vi represents the ratio of the initial velocities for the non-inhibited and inhibited reactions at a given substrate concentration [S], and sigma is the [S]/Km ratio. The procedure provides a simple way of determining the inhibition constants Ki and Ki', i.e, the dissociation constants of the EI and ESI complexes, respectively, and the velocity saturation values.