Lineweaver–Burk plot

An example of a Lineweaver-Burke plot.

In biochemistry, the Lineweaver–Burk plot (or double reciprocal plot) is a graphical representation of the Lineweaver–Burk equation of enzyme kinetics, described by Hans Lineweaver and Dean Burk in 1934.

Derivation

The plot provides a useful graphical method for analysis of the Michaelis–Menten equation:

$V = \frac{V_{\max} [S]}{K_m + [S]}$

Taking the reciprocal gives

${1 \over V} = {{K_m + [S]} \over V_{\max}[S]} = {K_m \over V_\max} {1 \over [S]} + {1 \over V_\max}$

where V is the reaction velocity (the reaction rate), K_m is the Michaelis–Menten constant, V_max is the maximum reaction velocity, and [S] is the substrate concentration.

Use

File:Inhibition diagrams.png

Lineweaver–Burk plots of different types of reversible enzyme inhibitors. The arrow shows the effect of increasing concentrations of inhibitor.

The Lineweaver–Burk plot was widely used to determine important terms in enzyme kinetics, such as K_m and V_max, before the wide availability of powerful computers and non-linear regression software. The y-intercept of such a graph is equivalent to the inverse of V_max; the x-intercept of the graph represents −1/K_m. It also gives a quick, visual impression of the different forms of enzyme inhibition.

The double reciprocal plot distorts the error structure of the data, and it is therefore unreliable for the determination of enzyme kinetic parameters. Although it is still used for representation of kinetic data, non-linear regression or alternative linear forms of the Michaelis–Menten equation such as the Hanes-Woolf plot or Eadie–Hofstee plot are generally used for the calculation of parameters.

When used for determining the type of enzyme inhibition, the Lineweaver–Burk plot can distinguish competitive, non-competitive and uncompetitive inhibitors. Competitive inhibitors have the same y-intercept as uninhibited enzyme (since V_max is unaffected by competitive inhibitors the inverse of V_max also doesn't change) but there are different slopes and x-intercepts between the two data sets. Non-competitive inhibition produces plots with the same x-intercept as uninhibited enzyme (K_m is unaffected) but different slopes and y-intercepts. Uncompetitive inhibition causes different intercepts on both the y- and x-axes .

Problems with the method

The Lineweaver–Burk plot is classically used in older texts, but is prone to error, as the y-axis takes the reciprocal of the rate of reaction – in turn increasing any small errors in measurement. Also, most points on the plot are found far to the right of the y-axis (due to limiting solubility not allowing for large values of [S] and hence no small values for 1/[S]), calling for a large extrapolation back to obtain x- and y-intercepts.

See also

• Michaelis–Menten kinetics
• Eadie–Hofstee diagram
• Hanes–Woolf plot

External links

• NIH guide, enzyme assay development and analysis