Photosynthetic activity of isolated chloroplasts from Euglena gracilis.

Functional chloroplasts from photoheterotrophic Euglena gracilis can be isolated in isoosmotic gradients of 10-80% Percoll. The chloroplasts display rates of CO2 dependent O2 evolution and CO2 fixation of 30-50 μmol mg(-1) chlorophyll h(-1) or 25-35% of the net O2 evolution by the whole cells and appear to be strikingly different from spinach chloroplasts in several respects: 1. tolerance to high concentration of orthophosphate in the assay medium; 2. inability to support oxaloacetate-dependent O2 evolution; 3. ability to support only low to moderate rates of 3-phosphoglycerate-dependent O2 evolution; 4. an apparent absence of a phosphate translocator in the terms described by Heldt and Rapley ([1970] FEBS Lett. 10, 143-148).