Potential Role of Pyrophosphate:Fructose 6-Phosphate Phosphotransferase in Carbohydrate Metabolism of Cold Stored Tubers of Solanum tuberosum cv Bintje
- 1 April 1991
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 95 (4), 1243-1249
- https://doi.org/10.1104/pp.95.4.1243
Abstract
To gain a better understanding of the mechanism of cold induced sweetening, sugar accumulation in potato, Solanum tuberosum cv Bintje, was compared to the maximum activity of inorganic pyrophosphate (PPi):fructose 6-phosphate 1-phosphotransferase (EC 2.7.1.90) and the concentration of two regulatory metabolites. Mature tubers accumulated reducing sugars and sucrose at an almost linear rate of 13.4 and 5.2 micromole per day per gram dry weight at 2°C and 4.5 and 1.3 micromole per day per gram dry weight, respectively, at 4°C. During storage at 8°C sugar accumulation was nil. Sugar accumulation was preceded by a lag phase of about 4 days. The accumulation of reducing sugars persisted for at least 4 weeks, whereas sucrose accumulation declined after 2 weeks of storage. The ratio of glucose:fructose changed concomitantly with sugar increase from 65:35 to equimolarity. The maximum activity of PPi:fructose 6-phosphate 1-phosphotransferase was 2.51 and 2.25 units per gram dry weight during storage at 2 and 8°C, respectively. The temperature coefficient of this enzyme from potatoes kept at 2 or 8°C was 2.12 and 2.48, respectively. The endogenous concentration of fructose 2,6-biphosphate increased from 0.15 to 1 nanomole per gram dry weight during storage at 2 and 4°C but remained the same throughout storage at 8°C. After exposure to 2°C an initial increase in the concentration of PPi was observed from 4.0 to 5.6 nanomoles per gram dry weight. Pyrophosphate concentration did not change during storage at 4°C but decreased slightly at 8°C. All observed changes became annulled after transfer of cold stored tubers to 18°C. These data strongly indicate that PPi:fructose 6-phosphate 1-phosphotransferase can be fully operational in cold stored potato tubers and the lack of increase in PPi concentration supports the functioning of this enzyme during sugar accumulation.Keywords
This publication has 8 references indexed in Scilit:
- Product Inhibition of Potato Tuber Pyrophosphate:Fructose-6-Phosphate Phosphotransferase by Phosphate and PyrophosphatePlant Physiology, 1989
- Molecular Comparison of Pyrophosphate- and ATP-Dependent Fructose 6-Phosphate 1-Phosphotransferases from Potato TuberPlant Physiology, 1988
- Fructose 2,6-Bisphosphate and Plant Carbohydrate MetabolismPlant Physiology, 1987
- Phosphofructokinase Activities in Photosynthetic OrganismsPlant Physiology, 1983
- A Kinetic Study of Pyrophosphate: Fructose‐6‐Phosphate Phosphotransferase from Potato TubersEuropean Journal of Biochemistry, 1982
- A special fructose bisphosphate functions as a cytoplasmic regulatory metabolite in green leavesProceedings of the National Academy of Sciences, 1982
- Changes in Potato Tuber Invertase and Its Endogenous Inhibitor After Slicing, Including a Study of Assay MethodsPlant Physiology, 1977
- A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye BindingAnalytical Biochemistry, 1976