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Light-driven Enzymatic Decarboxylation
Published on: May 22, 2016
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Glyoxylate decarboxylation during photorespiration
1Department of Botany, Botany School, University of Cambridge, CB2 3EA, Cambridge, U.K..
Planta
|January 11, 2014
Summary
Spinach leaf peroxisomes release CO2 from glycollate metabolism. This photorespiratory CO2 likely arises from glyoxylate decarboxylation, influenced by hydrogen peroxide and catalase.
Area of Science:
- Plant Physiology
- Biochemistry
- Photosynthesis Research
Background:
- Glycollate metabolism is central to photorespiration in plants.
- Peroxisomes play a key role in processing glycollate, but the precise mechanisms of CO2 release are debated.
Purpose of the Study:
- To investigate the source of CO2 released during glycollate oxidation in spinach leaf peroxisomes.
- To elucidate the role of glyoxylate and hydrogen peroxide in this process.
Main Methods:
- Incubation of spinach leaf peroxisomes with [1-(14)C]glycollate under aerobic conditions.
- Addition of glutamate, glycine, isonicotinyl hydrazide (INH), and catalase.
- Use of a model system with glucose oxidase to generate H2O2.
- Co-incubation of peroxisomes with illuminated chloroplasts.
Main Results:
- CO2 release from [1-(14)C]glycollate oxidation was observed in spinach leaf peroxisomes.
- Glutamate significantly increased glycollate conversion to glycine and CO2 release.
- CO2 release was attributed to glyoxylate decarboxylation, potentially involving H2O2, and was reduced by catalase.
- Light-activated chloroplasts enhanced glycollate decarboxylation and reduced glycine synthesis in a peroxisome-chloroplast mixture.
Conclusions:
- Glyoxylate decarboxylation in leaf peroxisomes is a critical branch point in the glycollate pathway.
- A portion of photorespired CO2 originates from glyoxylate decarboxylation, mediated by H2O2.
- Peroxisomal catalase may have a peroxidative role in this CO2 release mechanism.
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