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Aspartokinase from wheat germ: isolation, characterization, and regulation
1Department of Biology, Queen's University, Kingston, Ontario, Canada.
Plant Physiology
|February 1, 1973
Summary
Wheat germ aspartokinase requires ATP and metal ions for activity. This plant enzyme exhibits concerted feedback inhibition by lysine and threonine, suggesting a regulatory role.
Area of Science:
- Biochemistry
- Plant physiology
- Enzymology
Background:
- Aspartokinase is a key enzyme in the biosynthesis of aspartate-derived amino acids.
- Understanding plant aspartokinase is crucial for comprehending amino acid metabolism in crops.
Purpose of the Study:
- To isolate and characterize aspartokinase from wheat germ.
- To investigate the enzyme's kinetic properties and regulatory mechanisms.
Main Methods:
- Enzyme isolation and partial purification from wheat germ.
- Enzyme activity assays with varying substrates and effectors.
- Determination of kinetic parameters (Km) and inhibition patterns.
Main Results:
- Aspartokinase demonstrated an absolute requirement for ATP and divalent metal ions (Mg2+ or Mn2+).
- Lysine and threonine exhibited concerted feedback inhibition and stabilization against heat inactivation.
- Kinetic analysis revealed specific Km values for aspartate, ATP, and MgCl2.
Conclusions:
- Wheat germ aspartokinase functions as a regulatory enzyme.
- The enzyme displays a concerted feedback inhibition mechanism involving lysine and threonine.
- This regulation is vital for controlling aspartate-derived amino acid pathways in plants.