Glycolate and Glyoxylate Metabolism by Isolated Peroxisomes or Chloroplasts

Kisaki, Takuro; Tolbert, N. E.

doi:10.1104/pp.44.2.242

Cited by 149 publications

(55 citation statements)

References 22 publications

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“…The site-specific location of this irreversible transaminase has been shown for leaf peroxisomes (41), but it was reported absent in castor bean microbody preparations (6,17). In the present studies we found that this transaminase was present in microbodies of sunflower cotyledons (Fig.…”

supporting

confidence: 72%

Development of Microbodies in Sunflower Cotyledons and Castor Bean Endosperm during Germination

1971

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In cotyledons of sunflower seedlings glyoxysomal and peroxisomal enzymes exhibit different rates of development during germination. The total activity of isocitrate lyase, a glyoxysomal marker enzyme, rapidly increased during the first 3 days, and then decreased 89% by day 9. Exposure to light accelerated this decrease only slightly. The specific activity of glyoxysomal enzymes (malate synthetase, isocitrate lyase, citrate synthetase, and aconitase) in the microbody fraction from sucrose density gradients increased between days 2 and 4 about 2-to 3-fold, and thereafter it remained about constant in light or darkness.Total activity of the peroxisomal enzymes increased slowly in the dark during the first 4 days of germination and thereafter remained at a constant level of activity in the dark or increased 2-fold in 24 hours of light. The specific activties of glycolate oxidase, hydroxypyruvate reductase, and serine-glyoxylate aminotransferase in the isolated microbody fraction increased about 10-fold between days 2 and 4 in the dark and then remained constant or increased again 10-fold after an additional 48 hours in the light.The total activity of the common microbody marker, catalase, developed similarly to isocitrate lyase, but decreased only 72 % by day 9. The specific activities of enzymes (catalase, malate dehydrogenase, and aspartate aminotransferase) common to both microbody systems were 10-to 1000-fold greater than those of other enzymes. It is proposed that malate and aspartate may be involved in hydrogen transport between microbodies and other cellular sites.Glutamate-glyoxylate aminotransferase was very active in microbodies from castor bean endosperm and sunflower cotyledons. The specific activity of this aminotransferase developed similarly to glyoxysomal enzymes in the dark but further increased in the light, as did peroxisomal enzymes.The microbody fraction of castor bean endosperm germinated in the dark for 5 days contained both glyoxysomal and peroxisomal enzymes of similar specific activity.Adjacent to the microbody fraction on sucrose gradients from sunflower cotyledons were etioplasts at slightly lower densities and protein bodies at similar and higher densities. Their presence in the microbody fractions resulted in artificially low specific activities.

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confidence: 72%

Development of Microbodies in Sunflower Cotyledons and Castor Bean Endosperm during Germination

1971

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“…The label remaining in glycolate was four times greater when the compound was fed in the dark compared with the light feeding levels, suggesting that either: (a) glycolic acid metabolism is facilitated by light, or (b) uptake was ATP-limited so that a portion of the glycolate was not reaching cell organelles active in its metabolism. Since glycolate metabolism is largely restricted to glyoxysomes (18), an ATP-dependent transport process could limit the movement of fed glycolate to these organelles. However, since there is little reason to believe that glycolate transport is energy-dependent, it seems more likely that glycolate oxidation is light-influenced.…”

Section: Resultsmentioning

confidence: 99%

“…The partitioning of the reactions among organelles has already been considered elsewhere (18), but it is important to recognize that spatial separation of alternative control functions provides time lags which will serve to damp perturbations caused by external transients. If, as our studies indicate, there is a pathway from glyoxylate to malate in leaves, the glycolate pathway represents a couple among the light reactions, the Calvin cycle, "fatty acid" metabolism, and amino acid metabolism, in addition to the obvious couple with pyridine and adenine nucleotide-dependent reactions.…”

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confidence: 99%

Photosynthesis and Photorespiration in Typha latifolia

McNaughton

Fullem

1970

Plant Physiol.

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NaH'4CO3 (105 Cpm) to 1.3 ml of the enzyme preparation. At intervals, 0.4-ml samples were removed and acidified with 0.1 ml of 6 N acetic acid. Controls consisted of a zero time sample that was acidified immediately upon mixing the reaction components, and a reaction mixture lacking ribulose-1, 5-diP which was acidified at the end of the experimental period. The same enzyme preparation procedure was used for phosphopyruvate carboxylase except that dithioerythritol was sometimes substituted for reduced glutathione to provide an alternative test for sulfhydryl protection. The assay system for this enzyme, after Slack and Hatch (25), contained 1.55 ,umoles of phosphopyruvate and 15 ,umoles of sodium glutamate in substitution for the ribulose-1,5-diP used above. Controls were the same. For the assay of glycolate oxidase activity, leaves were homogenized in 0.067 M phosphate buffer (pH 7.8) and filtered through four layers of 60 mesh cheesecloth. This homogenate was used directly in a polarographic assay (10) with the Clark electrode. The reaction was initiated by adding 10 .moles of sodium glycolate in 0.2 ml of the phosphate buffer to 2.8 ml of the enzyme preparation. Controls were samples to which no glycolate was added. Addition of the enzyme cofactor, flavin mononucleotide, was not found to be stimulatory, and this was omitted from the assay system. Reagents were from Sigma.For "4CO0 assimilation experiments, leaves were preilluminated in 2 X 106 ergs cm-2 sec-l of light with their base in distilled water or a glycolate oxidase inhibitor, 0.01 M a-hydroxypyridinemethanesulfonic acid (Aldrich), for 30 min prior to release of "4CO2 by the acidification of a bicarbonate solution. Carbon dioxide concentration was 370 ,ul liter-' after addition of bicarbonate, to eliminate artifacts arising from high CO2 concentrations. Following 10 min of photosynthesis with water or 20 min with the inhibitor, the leaves were killed with boiling 80%-ethanol. In the controls, 1.8 AC of "CO, were used. In the experiments with inhibitor, 2.02 ,C of "CO2 were used. The different time periods and specific radioactivities of "CO2 were used to assure that approximately the same amount of radioactivity would be recovered from chromatograms of both treatments without overloading with plant extracts. Total cpm recovered from chromatograms per g of leaf extracted were 43,200 + 21,600 (0.95 confidence interval) for the water controls and 53,600 + 8,300 for experiments in inhibitor. For

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“…Some glycine may be decarboxylated directly without involving serine formation. Also glyoxylate may be transaminated with serine (thus bypassing glycine) to yield hydroxypyruvate in leaves (6). A transamination reaction between glycine and hydroxypyruvate to form serine is known to be catalyzed by leaf extracts (16), and this would result in a glycine to serine conversion in the absence of the serine hydroxymethyltransferase reaction.…”

Section: Resultsmentioning

confidence: 99%

“…Hence, it seemed unlikely that the decarboxylation of glyoxylate could occur by such a mechanism in the peroxisomes, although it might occur elsewhere in the cell. They suggested instead (6,7) that the glycolate pathway (11,15) must first produce glycine (Fig. 1), and that the CO2 is released during the complex hydroxymethyltransferase condensation of two glycine molecules to produce serine.…”

mentioning

confidence: 99%

Comparison of the Effectiveness of Glycolic Acid and Glycine as Substrates for Photorespiration

Zelitch

1972

Plant Physiol.

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Considerable evidence exists that the carboxyl-carbon atom of glycolic acid is the primary source of the C02 produced during photorespiration by leaves of many species of plants, including tobacco. Experiments were conducted to determine whether glyoxylate or glycine, both products of glycolic acid metabolism, is the more immediate precursor of photorespiratory C02.Illuminated tobacco leaf disks were floated on 18 mMsolutions of glycolate-1-YC or glycine-1-C in COrfree air. The "CO2 released and the "C content of several postulated intermediates were determined when the substrate solutions were provided alone or with one of the following: 9 mM a-hydroxy-2-pyridinemethanesulfonic acid, an inhibitor of the oxidation of glycolate to glyoxylate; 9 mM isonicotinyl hydrazide, an inhibitor of the conversion of glycine to serine; or 18 mmnonradioactive glycine or glycolate with the other radioactive substrate.Both inhibitors decreased the rate of photorespiration in tobacco leaf disks by the "C-assay. The a-hydroxy-2-pyridinemethanesulfonic acid severely blocked '4CO2 production and labeling of the glycolate pathway from glycolate-1-"C. Isonicotinyl hydrazide had little effect on the "CO2 released from glycine-l-'4C although the glycine to serine conversion was severely inhibited.These results and other data in the literature indicate that the glycolate pathway of carbohydrate metabolism does not supply sufficient C02 during the synthesis of serine from glycine to account for the rates of photorespiration observed in many species. A direct decarboxylation of glyoxylate is more likely the main source of photorespiratory C02.Ample evidence exists that the large quantities of CO2 produced in many photosynthetic tissues in the light arise primarily from the carboxyl-carbon atom of glycolic acid, an early product of photosynthesis (1, 2). This evidence comes from experiments showing parallel effects on glycolate metabolism and photorespiration brought about by changes in the oxygen and CO2 concentrations in the ambient atmosphere, the use of biochemical inhibitors and "C-labeled metabolites on intact tissues, and assays of enzyme activities in leaf extracts and in isolated leaf organelles (4,5,23 (ref. 23, pp. 204-208).

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Glycolate and Glyoxylate Metabolism by Isolated Peroxisomes or Chloroplasts

Cited by 149 publications

References 22 publications

Development of Microbodies in Sunflower Cotyledons and Castor Bean Endosperm during Germination

Development of Microbodies in Sunflower Cotyledons and Castor Bean Endosperm during Germination

Photosynthesis and Photorespiration in Typha latifolia

Comparison of the Effectiveness of Glycolic Acid and Glycine as Substrates for Photorespiration

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