The localization of glycollate-pathway enzymes in Euglena.
Isolation of organelles from broken-cell suspensions of phototrophically grown Euglena gracilis Klebs was achieved by isopycnic centrifugation on sucrose gradients. 2. Equilibrium densities of 1.23g/cm3 for peroxisome-like particles, 1.22g/cm3 for mitochondria and 1.17g/cm3 for chloroplasts were recorded. 3. The enzymes glycollate dehydrogenase, glutamate-glyoxylate aminotransferase, serineglyoxylate aminotransferase, aspartate-alpha-oxoglutarate aminotransferase, hydroxy pyruvate reductase and malate dehydrogenase were present in peroxisome-like particles. 4. Unlike higher plants glycollate dehydrogenase and glutamate-glyoxylate aminotransferase were present in the mitochondria of Euglena. 5. Rates of glycollate and  D-lactate oxidation were additive in the mitochondria, and, although glycollate dehydrogenase was inhibited by cyanide, D-lactate dehydrogenase activity was unaffected. 6. Glycollate oxidation was linked to O2 uptake in mitochondria but not in peroxisome-like particles. This glycollate-dependent O2 uptake was inhibited by antimycin A or cyanide. 7. The physiological significance of glycollate metabolism in Euglena mitochondria is discussed, with special reference to its role in photorespiration in algae.
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D001219:Aspartate Aminotransferases / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005055:Euglena / Q000201:enzymology* / Q000648:ultrastructure; D005649:Fumarate Hydratase / Q000378:metabolism; D006016:Glycolates / Q000378:metabolism*; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008830:Microbodies / Q000201:enzymology; D008928:Mitochondria / Q000378:metabolism; D010101:Oxygen Consumption; D013385:Succinate Dehydrogenase / Q000378:metabolism; D000637:Transaminases / Q000032:analysis*
D006016:Glycolates; D000429:Alcohol Oxidoreductases; D007770:L-Lactate Dehydrogenase; D007521:Isocitrate Dehydrogenase; D013385:Succinate Dehydrogenase; D002950:Citrate (si)-Synthase; D000637:Transaminases; D001219:Aspartate Aminotransferases; D005649:Fumarate Hydratase