Introduction The Michaelis-Menten Mechanism

The simplest possible enzymatic reaction scheme was proposed in 1913 by Michealis and Menten. They assumed the molecule undergoing reaction (the substrate, S) is adsorbed reversibly on a specific site of the enzyme E to form a complex ES whose decomposition into product P is rate controlling. The scheme resembles that for unimolecular decomposition (see Chapter 14). 

The rate constants ki and k2 correspond to forward and reverse binding steps to the enzyme, and k3 describes the rate of decomposition to product. The essential assumption is that the complex concentration (ES) reaches steady state 

Equation 11.6 shows that Km corresponds to the substrate concentration at which the rate has fallen to half the maximum. The kinetic parameters Vmax and Vmax/KM can be obtained by least squares regression of v vs. [S] plots or graphically by linearizing Equation 11.6. 

Reciprocal plots of Michaelis-Menten Isotope Effects 

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