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Updated: Jul 17, 2026
09:42
Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Substrate product equilibrium on a reversible enzyme, triosephosphate isomerase
Sharon Rozovsky1, Ann E McDermott
1Department of Chemistry, Columbia University, New York, NY 10027, USA.
Summary
Triosephosphate isomerase primarily binds its ketone substrate, dihydroxyacetone phosphate, not reactive intermediates. This suggests the initial reaction step is the slowest in the glycolytic pathway.
Area of Science:
- Biochemistry
- Enzymology
- Metabolic pathways
Background:
- Triosephosphate isomerase is a key glycolytic enzyme catalyzing the interconversion of dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate.
- Enzymes are hypothesized to stabilize specific reaction intermediates or transition states to enhance catalytic efficiency.
- Understanding the bound species provides insights into enzyme mechanisms and reaction kinetics.
Purpose of the Study:
- To determine the identity and relative abundance of chemical species bound to triosephosphate isomerase during catalysis.
- To investigate whether triosephosphate isomerase preferentially stabilizes the ketone substrate, aldehyde product, or enediol intermediate.
- To elucidate the rate-limiting step in the triosephosphate isomerase reaction mechanism.
Main Methods:
- Utilized nuclear magnetic resonance (NMR) spectroscopy, including solid- and solution-state techniques.
- Employed 13C-enriched dihydroxyacetone phosphate as the substrate for enhanced NMR signal detection.
- Characterized enzyme-bound species under various sample conditions, including a wide temperature range (-60°C to 15°C).
Main Results:
- The ketone substrate, dihydroxyacetone phosphate, was identified as the predominant species bound to triosephosphate isomerase.
- This predominance was consistently observed across the tested temperature range.
- No evidence was found for preferential stabilization of the enediol intermediate or the aldehyde product.
Conclusions:
- Triosephosphate isomerase does not appear to preferentially stabilize the reactive enediol intermediate or the aldehyde product.
- The observed binding suggests that the initial proton abstraction from dihydroxyacetone phosphate is likely the rate-limiting step.
- This finding supports a catalytic mechanism where subsequent steps are faster than the initial substrate transformation.
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