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Heart phosphofructokinase: allosteric kinetics with fructose 6-sulfate
Biochemistry
|November 16, 1976
Summary
This study reveals how heart phosphofructokinase is allosterically regulated using fructose 6-sulfate. It demonstrates cooperative binding of ATP involving at least four enzyme subunits.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Allosteric regulation
Background:
- Heart phosphofructokinase (PFK) is a key glycolytic enzyme.
- Understanding its allosteric regulation is crucial for metabolic studies.
Purpose of the Study:
- To investigate the allosteric regulation of heart phosphofructokinase.
- To characterize the kinetic properties using an alternative substrate, fructose 6-sulfate.
Main Methods:
- Kinetic studies of heart phosphofructokinase at pH 6.9.
- Utilized fructose 6-sulfate as an alternative substrate.
- Analyzed allosteric ligand effects at high enzyme concentrations.
Main Results:
- Determined a Km for ATP binding of 8-10 μM with saturating AMP.
- ATP inhibition showed cooperativity involving at least four enzyme subunits (interaction coefficient of 3.5).
- Citrate, AMP, and fructose 6-sulfate modulated cooperativity and inhibition thresholds.
Conclusions:
- Allosteric kinetics of heart PFK can be studied at high enzyme concentrations with fructose 6-sulfate.
- ATP inhibition involves at least four subunits, while other ligands interact with fewer.
- Citrate and ATP inhibition exhibit synergistic effects.