Abstract
The addition of glyoxylate to tobacco (Nicotiana tabacum) leaf discs inhibited glycolate synthesis and photorespiration and increased net photosynthetic 14CO2 fixation. This inhibition of photorespiration was investigated further by studying the effect of glyoxylate on the stimulation of photosynthesis that occurs when the atmospheric O2 level was decreased from 21 to 3% (the Warburg effect). The Warburg effect is usually ascribed to the increased glycolate synthesis and metabolism that occurs at higher O2 concentrations. Photosynthesis in control discs increased from 59.1 to 94.7 micromoles of CO2 per gram fresh weight per hour (a 60% increase) when the O2 level was lowered from 21 to 3%, while the rate for discs floated on 15 millimolar glyoxylate increased only from 82.0 to 99.7 micromoles of CO2 per gram fresh weight per hour (a 22% increase). The decrease in the O2 sensitivity of photosynthesis in the presence of glyoxylate was explained by changes in the rate of glycolate synthesis under the same conditions.
The rate of metabolism of the added glyoxylate by tobacco leaf discs was about 1.35 micromoles per gram fresh weight per hour and was not dependent on the O2 concentration in the atmosphere. This rate of metabolism is about 10% the amount of stimulation in the rate of CO2 fixation caused by the glyoxylate treatment on a molar carbon basis. Glyoxylate (10 millimolar) had no effect on the carboxylase/oxygenase activity of isolated ribulose diphosphate carboxylase. Although the biochemical mechanism by which glyoxylate inhibits glycolate synthesis and photorespiration and thereby decreases the Warburg effect is still uncertain, these results show that cellular metabolites can regulate the extent of the Warburg effect.
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Selected References
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- Bowes G., Ogren W. L., Hageman R. H. Phosphoglycolate production catalyzed by ribulose diphosphate carboxylase. Biochem Biophys Res Commun. 1971 Nov 5;45(3):716–722. doi: 10.1016/0006-291x(71)90475-x. [DOI] [PubMed] [Google Scholar]
- Canvin D. T., Fock H. Measurement of photorespiration. Methods Enzymol. 1972;24:246–260. doi: 10.1016/0076-6879(72)24072-1. [DOI] [PubMed] [Google Scholar]
- Ku S. B., Edwards G. E. Oxygen Inhibition of Photosynthesis: I. Temperature Dependence and Relation to O(2)/CO(2) Solubility Ratio. Plant Physiol. 1977 May;59(5):986–990. doi: 10.1104/pp.59.5.986. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lorimer G. H., Badger M. R., Andrews T. J. D-Ribulose-1,5-bisphosphate carboxylase-oxygenase. Improved methods for the activation and assay of catalytic activities. Anal Biochem. 1977 Mar;78(1):66–75. doi: 10.1016/0003-2697(77)90009-4. [DOI] [PubMed] [Google Scholar]
- Oliver D. J., Zelitch I. Increasing photosynthesis by inhibiting photorespiration with glyoxylate. Science. 1977 Jun 24;196(4297):1450–1451. doi: 10.1126/science.867040. [DOI] [PubMed] [Google Scholar]
- Oliver D. J., Zelitch I. Metabolic regulation of glycolate synthesis, photorespiration, and net photosynthesis in tobacco by L-glutamate. Plant Physiol. 1977 Apr;59(4):688–694. doi: 10.1104/pp.59.4.688. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Robinson J. M., Gibbs M., Cotler D. N. Influence of pH upon the Warburg Effect in Isolated Intact Spinach Chloroplasts: I. Carbon Dioxide Photoassimilation and Glycolate Synthesis. Plant Physiol. 1977 Apr;59(4):530–534. doi: 10.1104/pp.59.4.530. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Robinson J. M., Gibbs M. Photosynthetic intermediates, the warburg effect, and glycolate synthesis in isolated spinach chloroplasts. Plant Physiol. 1974 Jun;53(6):790–797. doi: 10.1104/pp.53.6.790. [DOI] [PMC free article] [PubMed] [Google Scholar]