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Platelet AMP deaminase. Purification and kinetic studies
The Journal of Biological Chemistry
|October 25, 1981
Summary
Human platelet AMP deaminase exhibits sigmoidal kinetics, shifting to hyperbolic with ATP activation. Guanine nucleotide effects on AMP deaminase activity differ between sodium and potassium salts.
Area of Science:
- Biochemistry
- Enzymology
- Human Physiology
Background:
- AMP deaminase is a crucial enzyme in purine metabolism.
- Understanding its kinetics and regulation is vital for cellular energy balance.
Purpose of the Study:
- To purify AMP deaminase from human platelets.
- To characterize the enzyme's kinetic properties and regulatory mechanisms.
Main Methods:
- Homogeneous purification of AMP deaminase using phosphocellulose chromatography.
- Kinetic analysis of enzyme activity as a function of AMP concentration.
- Investigating the effects of ATP and GTP on enzyme kinetics.
Main Results:
- Purified AMP deaminase displayed sigmoidal kinetics with respect to AMP concentration.
- ATP activation transformed the sigmoidal plot to hyperbolic, yielding a Michaelis constant (Km) of 1.2 mM.
- GTP exhibited differential effects: activation followed by inhibition in NaCl, and pure inhibition in KCl.
Conclusions:
- Human platelet AMP deaminase exhibits allosteric regulation.
- ATP acts as a potent activator, altering the enzyme's substrate affinity.
- GTP's regulatory role is dependent on the ionic environment, suggesting complex physiological control mechanisms.