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Reformulation of the Michaelis–Menten Equation: How Enzyme-Catalyzed Reactions Depend on Gibbs Energy

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Brian J. Bozlee

Department of Chemistry, Hawaii Pacific University, Kaneohe, HI 96744-5297

J. Chem. Educ., 2007, 84 (1), p 106

DOI: 10.1021/ed084p106

Publication Date (Web): January 1, 2007

Section:

History, Education, and Documentation

Abstract

Textbooks in biochemistry universally present a simplified two-step reaction mechanism for enzyme-catalyzed reactions. Step 1 is formation of an enzyme–substrate complex and step 2 is breakdown of the complex to form product. It is usually emphasized that the rate of the second step is increased when the enzyme raises the Gibbs energy of the complex and lowers the Gibbs energy of the second transition state. In this article the well-known Michaelis–Menten rate law for enzyme-catalyzed reactions is combined with the Arrhenius equation to show how the rate of reaction depends on Gibbs energies of both the first and second transition states (G₂ and G₄, respectively) as well as the Gibbs energy of the enzyme–substrate complex (G₃). In this way it becomes easier to see the effect of the first step of the reaction mechanism on the overall reaction rate. In general the maximum velocity of the reaction (v_m) depends solely on the activation energy of the second step (G₄ - G₃) whereas the Michaelis constant (K_M) depends on all three Gibbs energies (G₂, G₃, and G₄). Both v_m and K_M affect the overall rate of reaction.

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Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Biochemistry

Keywords (Subject):

Enzymes

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Enzyme Catalysis and the Gibbs Energy
Addison Ault
Journal of Chemical Education2009 86 (9), 1069
- Enzyme Catalysis and the Gibbs Energy
  Addison Ault
  Journal of Chemical Education2009 86 (9), 1069
  Gibbs-energy profiles are often introduced during the first semester of organic chemistry, but are less often presented in connection with enzyme-catalyzed reactions. In this article I show how the Gibbs-energy profile corresponds to the characteristic ...
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