Analysis of Kinetic Data

To test whether an enzyme-catalyzed reaction follows the Michaelis-Menten law, an experimenter will usually measure the intitial rates of a series of reactions, all at the same enzyme concentration, but at different substrate concentrations. Because the initial [S] is known precisely, and the change in [S] versus t is almost linear in the initial stages, accurate data for V as a function of [S] can be obtained.

A Lineweaver-Burk plot (Figure 11.16) is obtained by inverting the Michaelis-Menten equation to obtain the following:

For a reaction obeying Michaelis-Menten kinetics, plotting 1/V versus 1/[S] should yield a straight line. As seen in Figure 11.16, V max and K M can also be obtained easily from such a plot.

A disadvantage of the Lineweaver-Burk plot is the long extrapolation necessary to determine K M. One way around this problem is to graph V versus V/[S] (called an Eadie-Hofstee plot). The result, shown in Figure 11.17, also yields a straight line for reactions obeying Michaelis-Menten kinetics. Here, the slope of the line is equal to -K M.

See also: Michaelis-Menten Kinetics, K M, k CAT, and k CAT/K M, Enzyme Inhibition, Lineweaver-Burke Plot, Eadie Hofstee Plot

INTERNET LINK: Enzyme Kinetics