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Subunit interactions in yeast glyceraldehyde-3-phosphate dehydrogenase
Biochemistry
|December 16, 1975
Summary
Yeast glyceraldehyde-3-phosphate dehydrogenase inactivation follows a two-state model, involving tetramer-dimer dissociation. NAD+ binding and enzyme activity are sensitive to structural changes and covalent modification.
Area of Science:
- Biochemistry
- Enzymology
- Protein dynamics
Background:
- Yeast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a crucial enzyme in glycolysis.
- Understanding its inactivation mechanisms is vital for metabolic studies.
Purpose of the Study:
- To elucidate the spontaneous inactivation mechanism of yeast GAPDH.
- To investigate the effects of structural perturbations and covalent modification on enzyme activity and NAD+ binding.
Main Methods:
- Two-state kinetic modeling
- Sedimentation analysis
- Hybridization studies
- Equilibrium dialysis
Main Results:
- Inactivation follows a tetramer-dimer dissociation model, with dimers inactivating irreversibly without NAD+.
- Structural changes alter NAD+ binding cooperativity and enzyme activity.
- Covalent modification of active-site sulfhydryl groups impacts activity via subunit interactions.
Conclusions:
- Ligand-induced sequential conformational changes, transferred across subunit domains, explain observed binding patterns and half-of-the-sites reactivity.
- Yeast GAPDH inactivation is a complex process influenced by quaternary structure and ligand interactions.