The Lineweaver-Burk plot, also known as a double reciprocal plot, is a graphical representation of the Lineweaver-Burk equation, which is a mathematical transformation of the Michaelis-Menten equation. This plot allows for the visual determination of key enzyme kinetic parameters, specifically the Michaelis constant (Km) and the maximum reaction rate (Vmax). Km reflects the substrate concentration at which the reaction rate is half of Vmax, offering insights into the enzyme’s affinity for its substrate. Calculation of Km from the plot involves identifying the x-intercept, which represents -1/Km. To obtain the Km value, the inverse of the absolute value of the x-intercept is calculated. For example, if the x-intercept is -0.5, then Km would be calculated as 1/0.5 = 2.
Determining Km from a Lineweaver-Burk plot provides a rapid and visual means of estimating enzyme kinetics. This method proves advantageous in visualizing the effects of different types of enzyme inhibitors. Competitive inhibitors, for instance, alter Km but not Vmax, while non-competitive inhibitors alter Vmax but not Km. The double reciprocal plot facilitates the clear differentiation of these inhibition types by observing changes in the intercepts and slopes of the lines. Historically, the Lineweaver-Burk plot was a standard method for estimating enzyme kinetic parameters before the widespread adoption of computer-based non-linear regression analysis.
