What does the x-intercept represent in a Lineweaver-Burke plot?

In a Lineweaver-Burke plot, which is a double reciprocal plot used to analyze enzyme kinetics, the x-intercept specifically represents -1/Km. This relationship arises from how the plot is constructed. The Lineweaver-Burke plot takes the form of 1/V = (Km/Vmax) * (1/[S]) + (1/Vmax).

In this equation, if you plot 1/V (the y-axis) against 1/[S] (the x-axis), the slope of the resulting line is Km/Vmax, the y-intercept is 1/Vmax, and the x-intercept is where the line crosses the x-axis (1/[S] = 0).

Since the x-intercept corresponds to the value of 1/[S] when the reaction rate is infinite (which doesn't physically happen), it’s mathematically represented as -1/Km. This means the greater the Km value, the closer the x-intercept will approach zero (on the negative side), reflecting less affinity of the enzyme for the substrate.

This interpretation provides insight into enzyme-substrate interactions and allows researchers to calculate crucial kinetic parameters from experimental data. Understanding this intercept is essential for enzyme kinetics interpretation and