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Characterization at the Molecular Level using Robust Biochemical Approaches of a New Kinase Protein
Published on: June 30, 2019
Spinach pyruvate kinase isoforms : partial purification and regulatory properties
1Laboratory of Chemical Biodynamics, University of California, Berkeley, California, 94720.
Plant Physiology
|February 1, 1984
Summary
Spinach leaves contain two pyruvate kinase isoforms with distinct metabolic regulation. One isoform responds to respiratory metabolism, while the other is linked to ammonia assimilation pathways.
Area of Science:
- Plant biochemistry
- Enzymology
Background:
- Pyruvate kinase (PK) is a key enzyme in glycolysis.
- Plant PK isoforms exhibit varied regulatory mechanisms.
Purpose of the Study:
- To characterize the kinetic properties and regulatory mechanisms of two spinach leaf pyruvate kinase isoforms.
- To elucidate the differential metabolic control of these isoforms.
Main Methods:
- Separation of isoforms using blue agarose chromatography.
- Enzyme kinetics analysis including K(m) and K(i)/K(a) determination.
- Assessment of regulatory metabolite effects (citrate, aspartate, glutamate).
Main Results:
- Two spinach PK isoforms were isolated, sharing similar pH profiles and substrate K(m) values.
- Both isoforms were inhibited by oxalate and ATP, and activated by AMP.
- Isoform 1 showed citrate inhibition (K(i) = 1.2 mM), typical of previously reported plant PKs.
- Isoform 2 was unaffected by citrate but regulated by aspartate (activator, K(a) = 0.05 mM) and glutamate (inhibitor, K(i) = 0.68 mM).
Conclusions:
- The distinct regulatory profiles suggest differential roles for the two spinach PK isoforms.
- Isoform 1 likely responds to respiratory metabolism.
- Isoform 2 may be involved in regulating carbon skeletons for ammonia assimilation.
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