Lineweaver–Burk plot

The Lineweaver–Burk plot, also called the double-reciprocal plot, is a way of graphing enzyme kinetics data. The Michaelis–Menten equation describes how reaction rate (v) rises with substrate concentration ([S]) along a curve that levels off toward a maximum rate, Vmax. Because that curve only creeps toward Vmax, both Vmax and the Michaelis constant, Km, are hard to read from it. Taking the reciprocal of both sides of the equation gives a straight line, and in 1934 Hans Lineweaver and Dean Burk proposed plotting 1/v on the y-axis against 1/[S] on the x-axis.

On this line the y-intercept equals 1/Vmax, the x-intercept equals −1/Km, and the slope equals Km/Vmax. The plot is especially handy for telling types of enzyme inhibition apart. A competitive inhibitor raises the apparent Km but leaves Vmax unchanged, so lines drawn with and without it cross on the y-axis. A pure noncompetitive inhibitor lowers Vmax without changing Km, so the lines meet on the x-axis while the inhibited line sits higher. An uncompetitive inhibitor gives parallel lines.

The method has a known weakness: taking reciprocals magnifies errors in the slowest rates, measured at low substrate levels, and those points pull hardest on the line. Researchers now usually fit the original curve by computer, but the plot remains a favorite for displaying data and for exam questions.