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Crystallographic binding studies with triosephosphate isomerases: conformational changes induced by substrate and
R K Wierenga1, T V Borchert, M E Noble
1EMBL, Heidelberg, Germany.
FEBS Letters
|July 27, 1992
Summary
Triosephosphate isomerase (TIM) facilitates a simple proton transfer reaction. Crystallographic studies reveal substrate binding induces conformational changes, sealing the active site for efficient catalysis.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Triosephosphate isomerase (TIM) is a crucial enzyme in glycolysis.
- TIM catalyzes the reversible interconversion of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.
- Understanding TIM's mechanism is vital for metabolic pathway research.
Purpose of the Study:
- To elucidate the structural basis of TIM catalysis.
- To investigate the conformational changes upon substrate binding.
- To analyze the active site architecture in different organisms.
Main Methods:
- X-ray crystallography was employed to study TIM.
- Complex structures with substrate and analogues were determined.
- Comparative analysis of TIM structures from chicken, yeast, and trypanosome.
Main Results:
- TIM binds its substrate within a deep active site pocket.
- Substrate binding triggers significant conformational changes in three flexible loops.
- These changes result in the active site being shielded from the solvent.
- The catalytic glutamate residue is precisely positioned for proton transfer.
Conclusions:
- TIM employs a conformational selection mechanism for catalysis.
- Active site closure enhances catalytic efficiency and prevents side reactions.
- Structural insights provide a foundation for understanding TIM's role in metabolism.