| Pyridine and Adenine Nucleotide Status, and Pool Sizes of a Range of Metabolites in Chloroplasts, Mitochondria and the Cytosol/Vacuole of Avena Mesophyll Protoplasts during Dark/Light Transition: Effect of Pyridoxal Phosphate (1985) | |||||||||||||
Abstract | |||||||||||||
| Leaf mesophyll protoplasts of Avena sativa L. underwent dark/light transition in the absence or presence of pyridoxal phosphate (PLP), a specific inhibitor of the phosphate translocator of chloroplasts. By combining rapid fractionation of protoplasts with enzymatic cycling, the contents of metabolites (adenine nucleotides, pyridine nucleotides, triose phosphates, 3-phosphoglycerate, inorganic phosphate, aspartate, malate, oxaloacetate, glutamate, 2-oxoglutarate and citrate) associated with the chloroplasts, mitochondria and cytosol/vacuole were determined. Fluctuations of metabolite pools occurred in all compartments on illumination. Mitochondria showed immediate inhibition of their tricarboxylic acid cycle activities, as indicated by a transiently increased NADH/NAD+ ratio and elevated malate contents within 60 s of illumination. During this period large transient increases in triose phosphates took place in all fractions. Incubation of intact protoplasts with PLP severely affected the compartmented pool sizes, producing the typical pattern of inhibition of the chloroplast phosphate translocator. The mitochondrial pool sizes of the metabolites responded to light, if at all, differently than did the controls. | |||||||||||||
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