Effect of oxygen on Photosynthetic ^<14>CO_2 Fixation in Chroomonas sp. (Cryptophyta) : III. Effect of Oxygen on Photosynthetic Carbon Metabolism

概要

論文の詳細を見る
Photosynthetic carbon metabolism was studied with Chroomonas sp. cells in which the rate of photosynthesis was inhibited under both an anaerobic condition and high concentrations of oxygen. The time course of ^<14>C-incorporation into photosynthetic products showed that 3-phosphoglycerate was the initial product of photosynthetic CO_2 fixation in Chroomonas sp. cells. During 5-min photosynthesis, a considerable amount of ^<14>C was incorporated into the insoluble fraction (mostly cryptomonad starch), and oxygen predominantly affected ^<14>C-incorporation into this fraction. Although ^<14>C-incorporation into intermediates of the photorespiratory pathway increased with increasing O_2 concentration, the amounts were much less than expected from the degree of oxygen inhibition. It is noteworthy that ^<14>C-dihydroxyacetone phosphate accumulated during photosynthesis only under the anaerobic condition, whereas the levels of the other phosphate esters were scarcely affected by the oxygen concentration. Ribulose-1,5-bisphosphate carboxylase from Chroomonas sp. was competitively inhibited by oxygen, and its K_m(CO_2) value was similar to those of terrestrial C_3 plant enzymes.
日本植物生理学会の論文