Evidence of Reentrance of Glycolate Carbon into the Photosynthetic Carbon Reduction Cycle in Photosynthesizing Euglena gracilis Z.

Aminooxyacetate induced excretion of glycolate from air-grown cells of Euglena gracilis in both air and 1% CO(2) atmospheres. The rate of the excretion reached 70% of the photosynthetic rate in the air on a carbon basis, and was 10% in 1% CO(2). The compulsory loss of photosynthetically fixed carbon as glycolate at the high rate in air in the presence of aminooxyacetate caused a decrease of the rate of synthesis of paramylon, the reserve polysaccharide. Analyses of the steady levels of photosynthetic intermediates showed that a decrease of the 3-phosphoglycerate level was the cause of the slow rate of paramylon synthesis under these conditions.