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Conformational changes in bovine-liver glutamate dehydrogenase: a spin-label study
European Journal of Biochemistry
|June 1, 1979
Summary
Spin-labelled glutamate dehydrogenase shows altered reduction rates with L-glutamate. Electron spin resonance reveals conformational changes influenced by coenzyme binding and allosteric effectors like ADP and GTP.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Structural biology
Background:
- Glutamate dehydrogenase is a key metabolic enzyme.
- Understanding its conformational dynamics is crucial for metabolic regulation.
- Spin-labelling offers a sensitive method to probe enzyme structure.
Purpose of the Study:
- To investigate the conformational changes of glutamate dehydrogenase using a spin-labelled analogue.
- To correlate these changes with enzyme activity and allosteric regulation.
Main Methods:
- Utilized a spin-labelled p-chloromercuribenzoate analogue to modify glutamate dehydrogenase.
- Measured changes in enzyme activity (coenzyme reduction/oxidation rates).
- Analyzed electron spin resonance (ESR) spectra to probe enzyme conformation.
Main Results:
- A fivefold decrease in coenzyme reduction rate by L-glutamate was observed.
- No change in the oxidation rate by 2-oxoglutarate was detected.
- ESR spectra indicated complete conformational changes with saturating NADPH/substrates, but only partial changes with NADP+.
- Conformational changes upon NADPH binding occurred concertedly.
- The activator ADP and inhibitor GTP favored distinct enzyme conformations.
Conclusions:
- Electron spin resonance is a sensitive probe for glutamate dehydrogenase conformational states.
- Enzyme conformation is modulated by coenzyme binding and allosteric effectors.
- These findings provide insights into the allosteric regulation of glutamate dehydrogenase.