Triosephosphate isomerase, interconversion

The chemical reaction catalyzed by triosephosphate isomerase (TIM) was the first application of the QM-MM method in CHARMM to the smdy of enzyme catalysis [26]. The study calculated an energy pathway for the reaction in the enzyme and decomposed the energetics into specific contributions from each of the residues of the enzyme. TIM catalyzes the interconversion of dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde 3-phosphate (GAP) as part of the glycolytic pathway. Extensive experimental studies have been performed on TIM, and it has been proposed that Glu-165 acts as a base for deprotonation of DHAP and that His-95 acts as an acid to protonate the carbonyl oxygen of DHAP, forming an enediolate (see Fig. 3) [58]. 

The glycolytic enzyme triosephosphate isomerase (TIM) catalyzes the interconversion of the sugar phosphates dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde 3-phosphate (GAP). Although the reaction is extremely fast, the enzyme is an attractive candidate for mapping... 

The interconversion of the two triosephosphates is an essential step in the catabolism of carbohydrates (see chapter 12). Examining the catalytic mechanism of triosephosphate isomerase is instructive. It is among the enzymes that ap-... 

Dihydroxyacetone phosphate is converted to D-glyceraldehyde 3-phosphate by the enzyme triosephosphate isomerase as part of the glycolytic pathway of metabolism. Show how this interconversion could occur by a base-catalyzed mechanism ... 

An enzyme that has been the subject of intensive experimental and theoretical studies is triosephosphate isomerase (TIM), which catalyses the interconversion of dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde 3-phosphate (GAP), an essential step in the glycolytic pathway (Fersht 1985). The mechanism of the enzyme has been examined by QM/MM calculations which we do not describe here because it falls outside the topic ofthis review (Bash et al. 1991). However, an additional aspect of the overall mechanism is the conformational change of an 11-residue loop region (residues 166-176) which moves more than 7 A and closes over the active site when substrate binds (Joseph et al. 1990 Lolis et al. 1990). Mutagenesis experiments have... 

Triosephosphate isomerase is involved in the glycolytic pathway, and catalyzes the interconversion of dihydroxyacetone phosphate and D-glyceraldehyde phosphate (Fig. 17-27). The refined three-dimensional structures of chicken, yeast, and trypano-... 

Triosephosphate isomerase, for example, catalyzes the interconversion of glyceraldehyde 3-phosphate and dihydroxyacetone phosphate with fccat values that vary with pH, whereas is pH independent in the neutral range. This behavior appears consistent with mechanisms in which the enzyme combines with either monoanionic or dianionic forms of the substrate with similar affinity, but only the latter forms a productive complex, ES , which goes on to form products. Unlike an ordinary substrate analog, a transition-state analog for this reaction would be expected to be bound tightly only as a dianionic species, and this appears to be the case for the inhibitor 2-phosphoglycolic acid. ... 

The interconversion of n-glyceraldehyde-3-phosphate and dihydroxyacetone phosphate as catalyzed by triosephosphate isomerase involves proton abstraction from C3 of the ketonic substrate by an acid-base group of the enzyme to generate an enediol intermediate, followed by proton transfer from the acid-base group to C2 of the enediol to form the alde-... 

This enzyme [EC 5.3.1.1], also known as triosephosphate mutase (TIM) and phosphotriose isomerase, catalyzes the interconversion of D-glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (fUPAC glycerone phosphate). As pointed out by Rose, this enzyme is chiefly responsible for the largely symmetrical conversion of the two three-carbon segments of glucose to lactate and for the nearly uniform distribution of from pyruvate in the glucosyl units of hver glycogen. The... 

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