Human Biochemistry, Volume 1 - Murray R. 1993

Structure and Functions of Proteins and Enzymes
Enzymes: Mechanism of Action
Ordered and Random Substrate Binding

Many Enzymes catalyze reactions between two or more substrates, resulting in The formation of one or more products. Some enzymatic reactions require the simultaneous presence of all substrates. In other cases, the enzyme first interacts with one substrate and then catalyzes its reaction with another substrate. Substrate binding may occur in either a random or an ordered fashion (Fig. 9.8).

Many enzymatic reactions that strictly require the presence of Coenzymes proceed via a "ping-pong" (or shuttle) mechanism, in which the enzyme alternates between E and E' states (Figs. 9.9 and 9.10).

Although a coenzyme can often be regarded as a second substrate, some coenzymes are covalently bound to the enzyme or bound non-covalently, but so tightly that dissociation is practically non-existent (such as thiamine pyrophosphate). In these cases, we consider the entire enzyme-coenzyme complex to function as the enzyme.



Last update: 06/08/2026

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