EadieHofstee

Eadie-Hofstee refers to a graphical method used in enzyme kinetics to linearize the Michaelis-Menten relationship for single-substrate reactions. It is named after the scientists who introduced it, Eadie and Hofstee. The plot uses the variables v, the reaction velocity, and v/[S], where [S] is the substrate concentration.

The Eadie-Hofstee form of the Michaelis-Menten equation is v = Vmax − Km · (v/[S]). When v is plotted on the y-axis against v/[S] on the x-axis, the data should fall on a straight line. The y-intercept gives Vmax, and the slope gives −Km. The x-intercept occurs at v = 0, corresponding to a value of v/[S] = Vmax/Km. This representation allows estimation of the kinetic constants from experimental measurements of velocity at various substrate concentrations.

To construct the plot, researchers measure initial velocities v at several [S], compute v/[S], and perform linear regression on the set of (v/[S], v) points. Unlike some other plots, the Eadie-Hofstee plot uses all data points directly, which can reduce some distortions from relying on reciprocals of variables.

Strengths of the method include its use of raw velocity data and its relatively simple interpretation of the key parameters. Limitations include sensitivity to experimental error in v and [S], potential bias if data span a narrow range of [S], and the fact that any deviation from simple Michaelis-Menten behavior (e.g., allostery, inhibition) can complicate interpretation. Despite these caveats, the Eadie-Hofstee plot remains a classic tool in enzymology for estimating Km and Vmax.