General Themes in Enzymatic Mechanisms

The Proximity Effect Enzymes Bring Reacting Species Close Together 

General-Base and General-Acid Catalysis Avoids the Need for Extremely High or Low pH Electrostatic Interactions Can Promote the Formation of the Transition State Enzymatic Functional Groups Provide Nucleophilic and Electrophilic Catalysis Structural Flexibility Can Increase the Specificity of Enzymes 

Serine Proteases Enzymes that Use a Serine Residue for Nucleophilic Catalysis Ribonuclease A An Example of Concerted Acid-Base Catalysis 

The effectiveness of enzymes is due to the fact that they bring the reactants (substrates) together in a location where they are ideally oriented with respect to each other and the catalytic groups of the enzyme. 

I n chapter 7 we saw that enzymes can increase the rates of reactions by many orders of magnitude. We noted that enzymes are highly specific in the reactions they catalyze and in the particular substrates they accept. In this chapter we explore the mechanisms of several enzyme-catalyzed reactions in greater detail. Our goal is to relate the activity of each of these enzymes to the structure of the active site, where the functional groups of amino acid side chains, the polypeptide backbone, or bound cofactors must interact with the substrates in such a way as to favor the formation of the transition state. We explore enzyme catalytic mechanisms in many subsequent chapters as well but usually in less detail than here. 

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