Kinetics of Enzymatic Reactions Involving Two Substrates

1 Enzymes that catalyze reactions with two or more 7T) substrates work in a variety of ways. In some cases, the intermolecular reaction occurs when all the substrates are bound in a common enzyme-substrate complex in others, the substrates bind and react one at a time. A frequent application of kinetic measurements is to distinguish between such alternatives. 

Consider a reaction in which two substrates, S, and S2, are converted to products P and P2. One way for the reaction to occur is for S, to bind to the enzyme first, forming the binary complex ES,. Binding of S2 can then form the ternary complex ES,S2, which gives rise to the products 

This process is referred to as an ordered pathway. An alternative is a random-order pathway, in which the two substrates can bind to the enzyme in either order. Still another scheme is for Si to bind to the enzyme and be converted to 

Enzymes for Which kcat/Km Is Close to the Diffusion-Controlled Association Rate 

Source From Alan Fersht, Enzyme Structure and Mechanism, 3d ed. Copyright 1985 by W. H. Freeman Company, New York. Reprinted with permission. 

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The Henri-Michaelis-Menten Treatment Assumes That the Enzyme-Substrate Complex Is in Equilibrium with Free Enzyme and Substrate Steady-State Kinetic Analysis Assumes That the Concentration of the Enzyme-Substrate Complex Remains Nearly Constant Kinetics of Enzymatic Reactions Involving Two Substrates... 

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