Role of pyruvate kinase in non-specific changes of carbon photosynthetic metabolism, caused by the photophosphorylation inhibition]

The decrease in the level of NADP reduction in chloroplasts under injections of cofactors of pseudocyclic FMN photophosphorylation (vitamin K3 and methylviologen) into pea, tomato and cucumber leaves resulted in the decrease of 14CO2 autotrophic accumulation rate and in the change of distribution of assimilated carbon among the assimilation products. The inhibition of synthesis of labelled sugars and the increase of the content of 3-phosphoglyceric and glyceric acids in the labelled low molecular fraction were observed in all the experiments. Similar changes in the distribution of synthesized in Kalvin cycle labelled products, associated with the inhibition of its reduction unit, were observed under the effect of photophosphorylation uncoupling agents. However, the decrease of ATP/NADP ratio in chloroplasts resulted in the simultaneous increase of fixed 14CO2 incorporation into alanine. The role of pyruvate kinase in "alanine" effect, characteristic of non-specific changes of carbon photosynthetic metabolism, is discussed on the basis of the authors' previous data on the effect of phosphorylation on glycolysis reactions and on the basis of results of ADP introduction into leaf cuts.