Environmental regulation of enzymes in the microbodies and mitochondria of dark-grown, greening, and light-grown Euglena graclis

Catalase activity is demonstrated histochemically in the microbodies of aerated cultures of Euglena gracilis strain Z grown on inorganic media supplemented with acetate or glucose. Although this enzyme can also be assayed photometrically in cell-free extracts of acetate-supplemented cells, it is below the level of detectability in extracts of glucose-supplemented cells, there being an order of magnitude fewer microbodies in the latter than the former. Even acetate-supplemented cultures (dark-grown, greening, or continuously light-grown) fail to exhibit detectable catalase activity when CO₂ is removed from the air by Ascarite.Negative results were obtained with histochemical techniques considered optimal for the demonstration of cytochrome oxidase; under other conditions, however, a KCN-sensitive enzyme was revealed in the mitochondrial matrix. This (unidentified) enzyme is first observed in mitochondria after 20–24 hr of greening, reaches a maximum intensity at about 48 hr, and becomes undetectable by 72 hr of greening. Poisoning of photosynthesis by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) results in loss of activity of this mitochondrial enzyme.