Kinetics of Enzymatic Reactions: The Michaelis-Menten Equation

For users of the Mathcad browser: wmc-rmm1.mcd (23 KB, ver. 5.0)

The rate limiting step in the enzyme catalyzed transformation of substrate S into product P is the breakdown of the ES complex:

Since the ES concentration is not easily measured experimentally, Leonor Michaelis and Maud Menten have given an alternative expression for the determination of the rate of such enzymatic reactions: where KM, the Michaelis constant is defined as:

Several algebraic transformations to a linear form have been proposed for this equation which are more useful in the analysis of the experimental data: Lineweaver-Burk, Eadie and Dixon.

Given the following data for the hydrolysis of sucrose by the enzyme invertase, find which equation has the best correlation coefficient, determine the Michaelis constant and kb - the maximum turnover number:

[S]0.02920.05840.08760.1170.1460.1460.1750.234
k0.1820.2650.311 0.3300.349 0.3490.3720.371

In the Dixon expression, which has the best correlation, the substrate concentration [S] is correlated to the ratio of the substrate concentration [S] to the rate k. The maximum turnover number is the reciprocal of the slope, and the Michaelis constant is the product of the intercept with the maximum turnover number.

Question:

  1. Calculate the Michaelis constant and the maximum turnover number according the other two equations. Are the differences significant?

« Home » « Mathcad Menu »