During the course of NH4+ (or NO2-)-plus-alpha-oxoglutarate-dependent O2 evolution in spinach (Spinacia oleracea) chloroplasts, glutamate was continuously excreted out of the chloroplasts. Under these conditions, for each molecule of NO2- or NH4+ which disappeared, one molecule of glutamate accumulated in the medium and the concentration of glutamate in the stroma space was maintained constant. SO4(2-) (or SO3(2-) behave as inhibitors of NH4+ incorporation into glutamate by intact chloroplasts. This considerable inhibition of glutamate synthesis by SO4(2-) was correlated with a rapid decline in the stromal Pi concentration. The reloading of stromal Pi with either external Pi or PPi4- relieved SO4(2-)-induced inhibition of glutamate synthesis by intact chloroplasts. It was concluded that SO4(2-) induced a rapid efflux of stromal Pi out of the chloroplast, leading to a limitation of ATP synthesis and therefore to an arrest of ATP-dependent glutamine synthetase functioning.
Research Article|May 01 1989
Effect of sulphate on glutamate synthesis by intact spinach (Spinacia oleracea) chloroplasts
Biochem J (1989) 259 (3): 769-774.
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R Dumas, J Joyard, R Douce; Effect of sulphate on glutamate synthesis by intact spinach (Spinacia oleracea) chloroplasts. Biochem J 1 May 1989; 259 (3): 769–774. doi: https://doi.org/10.1042/bj2590769
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