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THE EFFECT OF MONOIODOACETIC ACID ON THE RESPIRATION AND PHOTOSYNTHESIS IN CHLORELLA. (DIE WIRKUNG VON MONOJODESSIGSAURE AUF ATMUNG UND PHOTOSYNTHESE VON CHLORELLA),
KANDLER (OTTO) MUNICH (WEST GERMANY)
The distribution of radioactivity after feeding labeled glucose, as well as the change of the pool-size of intermediates, in Chlorella poisoned with monoiodacetic acid MIA, showed that triosephosphate dehydrogenase is the most sensitive Enzyme in respiration. MIA leads to a large accumulation of fructose diphosphate FDP and a large decrease in phosphoglyceric acid PGA. Also, the breakdown of glucose via 6-phospho-gluconate is inhibited by MIA, as shown by the small change of the C1C6 ratio. FDP piles up during MIA poisoning in the dark and is quickly transformed to ribulose diphosphate RuDP, in the light subsequently, RuDP is transformed to PGA and its derivatives pyruvate and other acids by carboxylation and hydrolysis of the ketoacid. Thus, a third pathway of glucose breakdown, by passing glycolysis and the 6-phosphogluconate pathway, is induced by MIA in the light. The photosynthetic CO2 assimilation of Chlorella is about 100 fold more sensitive toward MIA than respiration. By feeding labeled CO2 and determining the concentration of the intermediates formed during MIA poisoning in the light, it is found that, in contrast to the behavior of broken chloroplasts, the reduction of the fixed CO2, is the most sensitive reaction of photosynthesis in Chlorella, rather than the formation of RuDP. Author
Pub. in Zeitschrift fur Naturforschung (West Germany) v16b n1 p50-61 1961 (Copies available only to DDC users). Text in German.
AF61 052 244