Abstract
This chapter discusses the use of pH studies to determine chemical mechanisms of enzyme-catalyzed reactions. The pH profiles that are of the most value are of pKi for competitive inhibitors or for metal-ion activators, log (V/K) for one or slower, nonsticky substrates, and isotope effects on V/K for these same substrates. Profiles of pKi for competitive inhibitors will show the required state of protonation of the inhibitor or of groups on the enzyme for binding. The log (V/K) versus pH profile for a nonsticky substrate shows the correct pK values of groups necessary for both binding and catalysis. Those pK values not present in the pKi profiles are groups that act as acid-base catalysts during the reaction, or whose protonation state is important for the chemical reaction, but not for binding. Profiles of V/K for nonsticky substrates can also be used in temperature-variation and solvent-perturbation studies to determine the nature of the groups involved.
Published Version
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