Mechanisms and Inhibitors

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  • 8.1 A Few Basic Catalytic Strategies Are Used by Many Enzymes

  • 8.2 Enzyme Activity Can Be Modulated by Temperature, pH, and Inhibitory Molecules

  • 8.3 Chymotrypsin Illustrates Basic Principles of Catalysis and Inhibition

Chess and enzymes have in common the use of strategy, consciously thought out in the game of chess and selected by evolution for the action of an enzyme. In the chess match depicted here, each player struggles to develop strategies to checkmate the opponent. Likewise, enzymes have catalytic strategies, developed over evolutionary time, for binding their substrates and chemically acting on them.

Thus far, in our study of enzymes, we have learned that an enzyme binds a substrate at the active site to facilitate the formation of the transition state; we have developed a kinetic model for simple enzymes; and we learned that allosteric enzymes are not only catalysts, but also information sensors. We now turn our attention to the catalytic strategies of enzymes and then to an examination of how enzyme activity can be altered by environmental factors distinct from allosteric signals. Finally, we will consider the catalytic mechanism of the digestive enzyme chymotrypsin, one of the first enzymes understood in mechanistic detail.