The localization of glycollate-pathway enzymes in Euglena

Abstract

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.

Submitochondrial Location and Some Properties of NAD+- and NADP+-Linked Malate Dehydrogenase inEuglena

“…Subfractionation of mitochondria was achieved by the method of Bandlow and Bauer l8 ) for yeast mitochondria using glycylglycine-KOH buffer, pH· 7.4. The vesicles of inner membrane and matrix were recovered at equilibrium density of 1.253 g/cm 3 • As shown in Table II, the activities of adenylate kinase and lactate dehydrogenase were located only in the intermembrane space and inner membrane, respectively, indicating that these fractions did not contaminate other submitochondrial fractions. Since the recovery of succinate semialdehyde dehydrogenase from purified mitochondria was 0.7,6.9, and 72.9% in the outer membrane, intermembrane space and matrix fraction, respectively, contaminations of matrix fraction into intermembrane space and outer membrane fractions were calculated to be 8.6 and 0.9%, respectively.…”

Studies on the Aminotransferases Participating in the Glycolate Metabolism of the Alga Mougeotia

“…In this organism, a microbody-associated glutamate-glyoxylate aminotransferase and a serine-glyoxylate aminotransferase are described (3).…”

Characterization of a Selenium-Independent Glutathione Peroxidase From Euglena gracilis

“…The organelles were lysed by a rapid freeze-thawing. The assay of marker enzymes has been described: succinate dehydrogenase and malate dehydrogenase (13), hydroxypyruvate reductase (4), and citrate synthetase (5).…”