INHIBITION OF PHOTOSYNTHETIC SUCROSE SYNTHESIS BY IMIDODIPHOSPHATE, AN ANALOG OF INORGANIC PYROPHOSPHATE

Autor(en): NEUHAUS, HE
STITT, M
Stichwörter: Biochemistry & Molecular Biology; FRUCTOSE-6-PHOSPHATE PHOSPHOTRANSFERASE; IMIDODIPHOSPHATE; LEAVES; METABOLISM; PHOSPHATE SYNTHASE; PHOTOSYNTHESIS; Plant Sciences; PLANTS; PYROPHOSPHATASE; SUBCELLULAR COMPARTMENTATION; SUCROSE SYNTHESIS
Erscheinungsdatum: 1991
Herausgeber: ELSEVIER SCI IRELAND LTD
Journal: PLANT SCIENCE
Volumen: 76
Ausgabe: 1
Startseite: 49
Seitenende: 55
Zusammenfassung: 
Imidodiphosphate, an analog of inorganic pyrophosphate (PP(i)), was supplied to illuminated, detached spinach leaves via the transpiration stream. It resulted in an accumulation of PP(i), depletion of uridine-5'-diphosphoglucose and other uridine nucleotides, and an increase in hexose-monophosphates, fructose-2,6-bisphosphate and fructose-1,6-bisphosphate. Sucrose synthesis was inhibited strongly, whereas starch synthesis was only weakly inhibited. The rate of CO2-saturated photosynthesis at limiting irradiance was not inhibited, but photosynthesis became saturated at lower irradiances and the maximal rate of photosynthesis was decreased in the presence of the analog. Imidodiphosphate also attenuated the secondary kinetics during induction of O2 evolution, which are typically associated with a limitation of photosynthesis by low rates of end-product synthesis. Relative to PP(i), imidodiphosphate was a poor substrate (forward reaction) and weak competitive inhibitor (reverse reaction) for pyrophosphate:fructose-6-phosphate phosphotransferase from potato tubers. It is argued that imidodiphosphate interferes with the turnover of PP(i) and the metabolism of uridine nucleotides in the cytosol, and it is suggested that it is unlikely that pyrophosphate fructose-6-phosphate phosphotransferase can play a cardinal role in removing the PP(i) which is formed during photosynthetic sucrose synthesis.
ISSN: 01689452

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