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Studies of cadmium binding to hexokinase: structural and functional implications
Rosa Olmo1, María Dolores Blanco, César Teijón
1Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain.
Journal of Inorganic Biochemistry
|April 5, 2002
Summary
Cadmium binding causes yeast hexokinase to aggregate without altering its active sites, maintaining high enzyme activity. This interaction results in mixed-type inhibition and negative cooperativity, impacting substrate binding.
Area of Science:
- Biochemistry
- Enzymology
- Protein Chemistry
Background:
- Yeast hexokinase is a crucial enzyme in glycolysis.
- Understanding its interaction with heavy metals like cadmium is important for cellular function and toxicology.
- Cadmium is a toxic metal that can interfere with various biological processes.
Purpose of the Study:
- To investigate the effects of cadmium on the structural and functional properties of yeast hexokinase.
- To elucidate the mechanism of cadmium-protein interaction and its impact on enzyme activity and kinetics.
Main Methods:
- Studied cadmium-yeast hexokinase interaction using techniques to assess protein aggregation and molecular mass.
- Analyzed changes in secondary structure using spectroscopic methods.
- Performed kinetic measurements with varying glucose and ATP concentrations.
- Conducted binding experiments at different temperatures to study cadmium-protein binding.
Main Results:
- Cadmium induced the formation of large protein aggregates without significant changes in secondary structure.
- Yeast hexokinase retained high enzymatic activity in both monomeric and aggregated forms.
- Cadmium exhibited mixed-type inhibition, primarily uncompetitive, with respect to glucose and ATP.
- Negative cooperative binding of cadmium to the protein was observed, with binding affinity decreasing at higher metal concentrations and temperatures.
Conclusions:
- Cadmium binding alters yeast hexokinase aggregation state but preserves active site integrity and enzymatic function.
- The aggregation process influences both metal and substrate binding sites, leading to altered enzyme kinetics.
- Labile interactions play a significant role in cadmium-protein binding, more so than specific interactions.