Book excerpt: Isotope effects have become one of the most powerful tools available to the enzymologist for probing enzymic mechanisms. Enzyme Mechanism from Isotope Effects presents the basic theory underlying isotope effects, including the latest findings on proton tunneling and coupled atomic notions. Specific theoretical applications are emphasized in regard to the types of information that can be obtained using isotope effects. The book also examines recent theoretical treatments of the product dependence of deuterium isotope effects, multiple isotope effects and isotope effects on intermediate partitioning. Other topics include a complete discussion of methods for measuring isotope effects, including a detailed description of the use of the isotope ratio mass spectrometer to obtain isotope effects, and a review of the literature regarding mechanistic information obtained from isotope effects for individual classes of enzyme-catalyzed reactions. Enzyme Mechanism from Isotope Effects is an excellent reference source for investigators using isotope effects in their research. The book is also valuable for reference libraries and instructors teaching courses in enzyme mechanism.