Abstract
Considerable evidence exists that the carboxyl-carbon atom of glycolic acid is the primary source of the CO2 produced during photorespiration by leaves of many species of plants, including tobacco. Experiments were conducted to determine whether glyoxylate or glycine, both products of glycolic acid metabolism, is the more immediate precursor of photorespiratory CO2.
Illuminated tobacco leaf disks were floated on 18 mm solutions of glycolate-1-14C or glycine-1-14C in CO2-free air. The 14CO2 released and the 14C content of several postulated intermediates were determined when the substrate solutions were provided alone or with one of the following: 9 mm α-hydroxy-2-pyridine-methanesulfonic acid, an inhibitor of the oxidation of glycolate to glyoxylate; 9 mm isonicotinyl hydrazide, an inhibitor of the conversion of glycine to serine; or 18 mm nonradioactive glycine or glycolate with the other radioactive substrate.
Both inhibitors decreased the rate of photorespiration in tobacco leaf disks by the 14C-assay. The α-hydroxy-2-pyridine-methanesulfonic acid severely blocked 14CO2 production and labeling of the glycolate pathway from glycolate-1-14C. Isonicotinyl hydrazide had little effect on the 14CO2 released from glycine-1-14C although the glycine to serine conversion was severely inhibited.
These results and other data in the literature indicate that the glycolate pathway of carbohydrate metabolism does not supply sufficient CO2 during the synthesis of serine from glycine to account for the rates of photorespiration observed in many species. A direct decarboxylation of glyoxylate is more likely the main source of photorespiratory CO2.
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Selected References
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- CALVIN M., MASSINI P. The path of carbon in photosynthesis. XX. The steady state. Experientia. 1952 Dec 15;8(12):445–457. doi: 10.1007/BF02139287. [DOI] [PubMed] [Google Scholar]
- Kisaki T., Tolbert N. E. Glycolate and glyoxylate metabolism by isolated peroxisomes or chloroplasts. Plant Physiol. 1969 Feb;44(2):242–250. doi: 10.1104/pp.44.2.242. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Osmond C. B., Harris B. Photorespiration during C 4 photosynthesis. Biochim Biophys Acta. 1971 May 11;234(2):270–282. doi: 10.1016/0005-2728(71)90082-x. [DOI] [PubMed] [Google Scholar]
- Tolbert N. E., Oeser A., Kisaki T., Hageman R. H., Yamazaki R. K. Peroxisomes from spinach leaves containing enzymes related to glycolate metabolism. J Biol Chem. 1968 Oct 10;243(19):5179–5184. [PubMed] [Google Scholar]
- Tolbert N. E., Yamazaki R. K. Leaf peroxisomes and their relation to photorespiration and photosynthesis. Ann N Y Acad Sci. 1969 Dec 19;168(2):325–341. doi: 10.1111/j.1749-6632.1969.tb43119.x. [DOI] [PubMed] [Google Scholar]
- VICKERY H. B. The metabolism of the organic acids of tobacco leaves. XIV. On the uptake of (+)-tartaric acid from solutions in the range pH 3 to pH 6. J Biol Chem. 1957 Aug;227(2):943–949. [PubMed] [Google Scholar]
- Wang D., Waygood E. R. Carbon metabolism of C-labeled amino acids in wheat leaves. I. A pathway of glyoxylate-serine metabolism. Plant Physiol. 1962 Nov;37(6):826–832. doi: 10.1104/pp.37.6.826. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ZELITCH I. THE RELATION OF GLYCOLIC ACID SYNTHESIS TO THE PRIMARY PHOTOSYNTHETIC CARBOXYLATION REACTION IN LEAVES. J Biol Chem. 1965 May;240:1869–1876. [PubMed] [Google Scholar]
- ZELITCH I. The relationship of glycolic acid to respiration and photosynthesis in tobacco leaves. J Biol Chem. 1959 Dec;234:3077–3081. [PubMed] [Google Scholar]
- ZELITCH I. The role of glycolic acid oxidase in the respiration of leaves. J Biol Chem. 1958 Dec;233(6):1299–1303. [PubMed] [Google Scholar]
- Zelitch I. BIOCHEMICAL CONTROL OF STOMATAL OPENING IN LEAVES. Proc Natl Acad Sci U S A. 1961 Sep;47(9):1423–1433. doi: 10.1073/pnas.47.9.1423. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zelitch I. Investigation on photorespiration with a sensitive C-assay. Plant Physiol. 1968 Nov;43(11):1829–1837. doi: 10.1104/pp.43.11.1829. [DOI] [PMC free article] [PubMed] [Google Scholar]