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Origin of acetate in spinach leaf cell
1Department of Biochemistry and Biophysics, University of California, Davis, California 95616.
Plant Physiology
|April 1, 1982
Summary
Spinach leaf mitochondria contain an enzyme that generates acetate from acetyl-CoA. This acetate is then used by chloroplasts to synthesize acetyl-CoA, a key metabolic intermediate.
Area of Science:
- Plant Biochemistry
- Mitochondrial Function
- Photosynthesis
Background:
- Mitochondria play a crucial role in cellular energy metabolism.
- Acetyl-CoA is a central intermediate in various metabolic pathways.
- The precise roles of mitochondrial enzymes in plant metabolism are still being elucidated.
Purpose of the Study:
- To identify and characterize enzymes involved in acetyl-CoA metabolism within spinach leaf mitochondria.
- To investigate the potential role of mitochondrial acetate production in plant metabolic regulation.
- To explore the inter-organelle transport and utilization of acetate between mitochondria and chloroplasts.
Main Methods:
- Isolation of highly pure mitochondria from spinach (Spinacia oleracea L.) leaves using Percoll gradient centrifugation.
- Enzyme activity assays to determine kinetic parameters (Km, Vmax) of the identified hydrolase.
- Electron microscopy and biochemical analyses to confirm organelle purity and enzyme localization.
Main Results:
- A short-chain acyl-coenzyme A hydrolase was identified in spinach leaf mitochondrial matrix.
- This enzyme efficiently converts acetyl-CoA to acetate and CoA (Km = 150 µM, Vmax = 140 nmol/mg protein/hr).
- Enzyme activity is product inhibited by CoA-sulfhydryl, but stimulated by specific disulfides.
Conclusions:
- Mitochondria can generate free acetate from acetyl-CoA, potentially from pyruvate metabolism.
- Free acetate may be rapidly transported to chloroplasts.
- Chloroplasts utilize this acetate via acetyl-CoA synthetase to produce acetyl-CoA for metabolic processes.