Eadie-Hofstee diagram

From Wikipedia, the free encyclopedia

In biochemistry, an Eadie-Hofstee diagram (also Woolf-Eadie-Augustinsson-Hofstee or Eadie-Augustinsson plot) is a graphical representation of enzyme kinetics in which reaction velocity is plotted as a function of the velocity vs. substrate concentration ratio:

$v = -K_m { v \over [S] } + v_{max}$

where v represents reaction velocity, K_m is the Michaelis-Menten constant, [S] is the substrate concentration, and v_max is the maximum reaction velocity.

It can be derived from the Michaelis-Menten equation as follows:

$v = {{v_{max} [S]} \over {K_m + [S]}}$

invert and multiply with $v m a x$ :

${v_{max} \over v} = {{v_{max}(K_m+[S])}\over{v_{max}[S]}} = {{K_m+[S]}\over{[S]}}$

Rearange:

$v_{max} = {{{vK_m} \over {[S]}} + {{v[S]} \over {[S]}}} = {{vK_m}\over {[S]}} + v$

Isolate V:

$v = -K_m{v \over {[S]}} + v_{max}$

Like other techniques that linearize the Michaelis-Menten equation, the Eadie-Hofstee plot allows for rapid identification of important kinetic terms like K_m and v_max. It is also more robust against error-prone data than the Lineweaver-Burk plot, particularly because it gives equal weight to data points in any range of substrate concentration or reaction velocity. (The Lineweaver-Burk plot unevenly weighs such points.)

One drawback from the Eadie-Hofstee approach is that neither ordinate nor abscissa represent independent variables: both are dependent on reaction velocity. Thus any experimental error will be present in both axes.

[edit] References

Eadie, GS (1942). "The Inhibition of Cholinesterase by Physostigmine and Prostigmine". Journal of Biological Chemistry 146: 85—93.

Hofstee, BHJ (1959). "Non-Inverted Versus Inverted Plots in Enzyme Kinetics". Nature 184: 1296—1298.

Dowd, JE, and Riggs, DS (1965). "A Comparison of Estimates of Michaelis-Menten Kinetic Constants from Various Linear Transformations". Journal of Biological Chemistry 240: 863—869.