Simultaneous Measurement of Oxygen Evolution and Endogenous Adenosine-Triphosphate Levels in Isolated ‘Intact’ Chloroplast Suspensions

Abstract

Simultaneous continuous polarographic estimation of oxygen evolution and measurement of ATP levels by the firefly luciferase method were made in suspensions containing predominantly intact spinach chloroplasts. Measurements were made during light to dark and dark to light transitions in the presence and absence of bicarbonate, 3-phosphoglycerate and ribose-5-phosphate and following the addition of these compounds during steady state conditions. Absolute levels of ATP were usually in the range 3.7 μmol ATP per g chlorophyll and the results of kinetic experiments are interpreted within the established concepts of photophosphorylation and the carbon reduction cycle. In experiments involving dark to light transitions in the absence of added bicarbonate, light to dark transitions in the presence of 3-phosphoglycerate and during photosynthesis in the presence of bicarbonate, 3-phosphoglycerate and ribose-5-phosphate rapid transient changes in ATP levels were observed.