MUCH ADO ABOUT ENZYME MECHANISMS

• Published in: Chemical & Engineering News Vol. 82; no. 8; p. 35
• Main Author: Borman, Stu
• Format: Trade Publication Article
• Language: English
• Published: Washington American Chemical Society 23.02.2004
• Subjects: Chemical reactions; Enzymes; R&D; Research & development; Theory; United States > US
• ISSN: 0009-2347; 1520-605X
• DOI: 10.1021/cen-v082n008.p035

According to transition-state theory, a stable reactant must surmount a free-energy barrier to be converted to a product. This barrier is the transition state, a species whose reacting bonds are midway to being formed or broken, as the case may be. transition states are dynamical bottlenecks to reaction, defining the critical point of no return where potentially reacting species convert to products or return to reactants. Enzymes can aid reactions by binding and lowering the energies of transition states, thus making it easier for enzyme substrates to traverse reaction paths. Most enzymologists believe this is the basic way most enzymes work - that transition-state binding and stabilization are primarily responsible for catalytic rate acceleration. However this view has been undergoing considerable refinement, as researchers study phenomena that may underlie, accompany, or even supersede transition-state stabilization - such as electrostatics, quantum mechanical tunneling, coupled protein motions, low-barrier hydrogen bonds, and near-attack conformations. Most of these refinements have themselves been subject to some degree of debate or controversy.