The folding pathway of triosephosphate isomerase.

Publisher Summary This chapter discusses the folding pathway of triosephosphate isomerase (TIM), which is a widely studied enzyme. The ubiquity, efficient catalytic activity, and (β/α)8 barrel three-dimensional conformation of this enzyme makes it an excellent model to perform almost any kind of research. TIM is a glycolytic enzyme that catalyzes the interconversion between glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP) in the fifth reaction of glycolysis. This reaction is catalyzed with high efficiency, and it is a diffusive process, which is limited only by the rate at which GAP encounters or departs from the active site. TIM is active only in the oligomeric form, and the structure of the native dimer suggests that the presence of both subunits is important for stabilizing the active-site residues. Each monomer contains catalytic residues and the loops at the carboxyl termini of the barrel form the interface among subunits. Protein denaturation is a natural and artificial process that involves the disruption of the three-dimensional organization of protein molecules, that is, the secondary, tertiary, and quaternary structures.