Occurrence and operation of the glycollate–glyoxylate shuttle in mitochondria of Euglena gracilis Z

Both glyoxylate reductase (NADP+) and glycollate dehydrogenase were located exclusively in mitochondria in Euglena gracilis and constitute the glycollate–glyoxylate shuttle, whose existence in higher plants was thought doubtful, owing to different subcellular locations of the two enzymes. Disrupted Euglena mitochondria showed a glycollate-dependent NADPH oxidation, indicating actual operation of the shuttle in this protozoon.

Download Full-text

Photometabolism of Glycollate by Euglena Gracilis

Australian Journal of Biological Sciences ◽

10.1071/bi9710023 ◽

1971 ◽

Vol 24 (1) ◽

pp. 23 ◽

Cited By ~ 16

Author(s):

David R Murray ◽

J Grovanelli ◽

Robert M Smillie

Keyword(s):

Carbon Source ◽

Euglena Gracilis ◽

Higher Plants ◽

Serine Hydroxymethyltransferase ◽

Single Source ◽

Photosynthetic Organisms ◽

Inhibition Of Growth ◽

Glycollate Oxidase ◽

Isonicotinyl Hydrazide ◽

Glyoxylate Reductase

The photometabolism of glycollate was investigated in E. gracilis, strain Z, an organism which can utilize glycollate as a single source of carbon in the light but not in the dark. The nature of the labelled products of the photometabolism of [1-14CJglycollate, [2_14CJglycollate, and [l-14CJglycine and the inhibition of growth on glycollate by isonicotinyl hydrazide and by ex-hydroxy-2-pyridine methane sul-phonate were consistent with the operation of a glycollate pathway of the type found in the leaves of higher plants. In addition, several enzymes associated with gly-collate metabolism in other photosynthetic organisms were demonstrated in cell-free extracts of E. gracilis grown with glycollate as the only carbon source. These included glycollate oxidase, NADPH: glyoxylate reductase, NADH: glyoxylate reductase (E.C.1.1.1.26), glycine transaminase (E.C.2.6.1.4), formyltetrahydro-folate synthetase (E.C. 6.3.4.3), and serine hydroxymethyltransferase (E.C. 2.1.2.1).

Download Full-text

Purification and some properties of glyoxylate reductase (NADP+) and its functional location in mitochondria in Euglena gracilis z

Biochemical Journal ◽

10.1042/bj2270211 ◽

1985 ◽

Vol 227 (1) ◽

pp. 211-216 ◽

Cited By ~ 17

Author(s):

A Yokota ◽

S Haga ◽

S Kitaoka

Keyword(s):

Gel Electrophoresis ◽

Glyoxylate Cycle ◽

Polyacrylamide Gel Electrophoresis ◽

Intermembrane Space ◽

Difference Spectra ◽

Inner Membrane ◽

Optimum Ph ◽

Glycollate Dehydrogenase ◽

Euglena Gracilis Z ◽

Glyoxylate Reductase

Euglena mitochondria contain both glyoxylate reductase (NADP+) and glycollate dehydrogenase to constitute the glycollate-glyoxylate cycle [Yokota & Kitaoka (1979) Biochem. J. 184, 189-192]. Euglena glyoxylate reductase (NADP+) was purified and its submitochondrial location was determined in order to elucidate the cycle. The purified glyoxylate reductase was homogeneous on polyacrylamide-gel electrophoresis. Difference spectra of the purified enzyme revealed that the enzyme was a flavin enzyme. The Mr of the enzyme was 82 000. The enzyme was specific for NADPH, with an apparent Km of 3.9 microM, and for glyoxylate, with an apparent Km of 45 microM. It was 30% as active with oxaloacetate as with glyoxylate. NADH and hydroxypyruvate did not support the activity at all. The optimum pH was 6.45. Submitochondrial fractionation of purified mitochondria showed that the enzyme was located in the intermembrane space and loosely bound to the outer surface of the inner membrane. These properties and the submitochondrial localization of NADPH-glyoxylate reductase facilitate the operation of the glycollate-glyoxylate cycle in combination with glycollate dehydrogenase, which is tightly bound to the inner membrane of Euglena mitochondria.

Download Full-text

The localization of glycollate-pathway enzymes in Euglena

Biochemical Journal ◽

10.1042/bj1480321 ◽

1975 ◽

Vol 148 (2) ◽

pp. 321-328 ◽

Cited By ~ 53

Author(s):

N Collins ◽

M J Merrett

Keyword(s):

Lactate Dehydrogenase ◽

Euglena Gracilis ◽

Higher Plants ◽

Antimycin A ◽

O2 Uptake ◽

Lactate Oxidation ◽

Lactate Dehydrogenase Activity ◽

Glycollate Dehydrogenase ◽

Glyoxylate Aminotransferase ◽

Isopycnic Centrifugation

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-α-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.

Download Full-text