Much ado about enzyme mechanisms

WHAT ARE THE UNDERLYING forces and mechanisms that enable enzymes to accelerate reactions? "Quite recently, we have found that there are enzymes that enhance reaction rates by factors as large as 1020-fold," says chemistry professor Richard V. Wolfenden of the University of North Carolina, Chapel Hill. "The challenge is to explain how they do this." Some contend that the issue is all decided—that enzymes generally catalyze reactions by stabilizing transition states (activated complexes), enabling reactants to convert easily to products. But it's frequently a lot more complicated than that. "It's a fairly heated-up subject right now," says chemistry professor Stephen J. Benkovic of Pennsylvania State University. "We're beginning to understand, after all, that transition-state binding is just a catch-phrase. Clearly, that's one way you have catalysis. But now we're getting a better idea of how it actually comes about." According to transition-state theory, a stable reactant must surmount a free-energy ...