Eadie–Hofstee diagram

Eadie–Hofstee diagram is a graphical representation used in enzyme kinetics, named after its developers, G. Eadie and B. G. Hofstee. It is a transformation of the Michaelis-Menten equation, which describes the rate of enzymatic reactions.

Overview

The Eadie-Hofstee diagram plots the reaction velocity (v) against the ratio of the velocity to the substrate concentration (v/[S]). The slope of the line in this plot is -Km, the Michaelis constant, and the y-intercept is Vmax, the maximum reaction velocity. This method is often used because it can provide accurate estimates of Km and Vmax, even when the data are somewhat noisy.

Derivation

The Eadie-Hofstee diagram is derived from the Michaelis-Menten equation:

v = Vmax[S]/(Km + [S])

By rearranging this equation, we obtain:

v = -Km(v/[S]) + Vmax

This is the equation of a straight line (y = mx + b), where y = v, x = v/[S], m = -Km, and b = Vmax. Thus, a plot of v against v/[S] gives a straight line with slope -Km and y-intercept Vmax.

Applications

The Eadie-Hofstee diagram is used in the study of enzyme kinetics to determine the values of Km and Vmax, which are important parameters in understanding the behavior of enzymes. It can also be used to identify different types of enzyme inhibition, as different inhibitors will cause different changes in the slope and y-intercept of the line.

Limitations

While the Eadie-Hofstee diagram is a useful tool in enzyme kinetics, it has some limitations. The main one is that it can be sensitive to experimental error, as small errors in the measurement of the reaction velocity can lead to large errors in the calculated values of Km and Vmax. In addition, it assumes that the Michaelis-Menten equation is a valid description of the enzyme-catalyzed reaction, which may not be the case for all enzymes.

See also

• Lineweaver–Burk plot
• Hanes–Woolf plot
• Enzyme kinetics
• Michaelis-Menten kinetics