Uses of isotope effects in the study of enzymes

There have been few recent additions to the technical methods employed in t he study of isotope effects, notable exceptions being the use of high press ure as an experimental variable and the measurement of heavy-atom isotope e ffects on maximal velocities using continuous-flow techniques. Most of the innovations are in the realm of new experimental designs that allow the ash ing of new questions. These designs include the use of isotope effects to: determine kinetic mechanisms, distinguish between changes in enzymatic acti vity and loss of active enzyme, distinguish between reactant-state origins and transition-state origins and quantify hydrogen tunneling, separate and quantify multiple origins of solvent isotope effects, distinguish between c oncerted and stepwise chemical mechanisms, characterize bond order changes in ligand binding, distinguish different pathways of inhibitor binding, and estimate intrinsic isotope effects. (C) 2001 Academic Press.