Lack of aconitase in glyoxysomes and peroxisomes

The aim of this work was to find out whether aconitase [citrate (isocitrate) hydro-lyase, EC 4.2.1.3] which is rapidly inactivated by H2O2, is present in the microbodies from plant cells. The separation of intact organelles from castor-bean (Ricinus communis) endosperm and potato (Solanum tuberosum) tuber indicated that aconitase activity is essentially limited to the mitochondria and cytosol fraction, but was not detected in highly purified castor-bean endosperm and potato tuber peroxisomes. An isotropic e.p.r. signal of the type expected for the 3Fe cluster of oxidized aconitase was not detected in microbodies. In immunoblot analyses, antibodies raised against potato tuber mitochondrial aconitase did not cross-react with any glyoxysomal or peroxisomal protein. Positive reactions were found for cytosol fraction and mitochondria of castor-bean endosperm. The operation of the full glyoxylate cycle in isolated glyoxysomes requires the presence of aconitase in the incubation medium. It is concluded that glyoxysomes are probably devoid of aconitase and that the glyoxylate cycle requires a detour via the cytosol, which contains a powerful aconitase activity.

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Autophagic Machinery of Plant Peroxisomes

International Journal of Molecular Sciences ◽

10.3390/ijms20194754 ◽

2019 ◽

Vol 20 (19) ◽

pp. 4754 ◽

Cited By ~ 4

Author(s):

Sławomir Borek ◽

Szymon Stefaniak ◽

Jan Śliwiński ◽

Małgorzata Garnczarska ◽

Małgorzata Pietrowska-Borek

Keyword(s):

Molecular Mechanisms ◽

Glyoxylate Cycle ◽

Plant Cells ◽

Physiological Role ◽

Signal Molecules ◽

Cell Organelles ◽

Selective Degradation ◽

Leaf Peroxisomes ◽

The Glyoxylate Cycle

Peroxisomes are cell organelles that play an important role in plants in many physiological and developmental processes. The plant peroxisomes harbor enzymes of the β-oxidation of fatty acids and the glyoxylate cycle; photorespiration; detoxification of reactive oxygen and nitrogen species; as well as biosynthesis of hormones and signal molecules. The function of peroxisomes in plant cells changes during plant growth and development. They are transformed from organelles involved in storage lipid breakdown during seed germination and seedling growth into leaf peroxisomes involved in photorespiration in green parts of the plant. Additionally, intensive oxidative metabolism of peroxisomes causes damage to their components. Therefore, unnecessary or damaged peroxisomes are degraded by selective autophagy, called pexophagy. This is an important element of the quality control system of peroxisomes in plant cells. Despite the fact that the mechanism of pexophagy has already been described for yeasts and mammals, the molecular mechanisms by which plant cells recognize peroxisomes that will be degraded via pexophagy still remain unclear. It seems that a plant-specific mechanism exists for the selective degradation of peroxisomes. In this review, we describe the physiological role of pexophagy in plant cells and the current hypotheses concerning the mechanism of plant pexophagy.

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Association of the glyoxylate cycle enzymes in a novel subcellular particle from castor bean endosperm

Biochemical and Biophysical Research Communications ◽

10.1016/s0006-291x(67)80007-x ◽

1967 ◽

Vol 27 (4) ◽

pp. 462-469 ◽

Cited By ~ 201

Author(s):

R.W. Breidenbach ◽

Harry Beevers

Keyword(s):

Castor Bean ◽

Glyoxylate Cycle ◽

The Glyoxylate Cycle

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Metabolite Oxidation and Transport in Mitochondria of Endosperm From Germinating Castor Bean

Functional Plant Biology ◽

10.1071/pp9830167 ◽

1983 ◽

Vol 10 (2) ◽

pp. 167 ◽

Cited By ~ 9

Author(s):

J Millhouse ◽

JT Wiskich ◽

H Beevers

Keyword(s):

Malic Enzyme ◽

Castor Bean ◽

Glyoxylate Cycle ◽

Density Gradients ◽

Metabolite Transport ◽

The Glyoxylate Cycle ◽

Exchange Properties ◽

Transport In Mitochondria

Mitochondria from germinating castor bean endosperm were purified on linear sucrose-density gradients. It is shown that succinate and malate plus glutamate are oxidized rapidly; other substrates including malate (via malic enzyme) and external NADH are oxidized slowly. It is proposed that the oxidation of NADH produced during β-oxidation and the glyoxylate cycle occurs intramitochondrially via malate. Castor bean mitochondria are relatively impermeable to oxaloacetate and a malate-aspartate type shuttle is required. Metabolite transport and exchange properties support the operation of malatein (or succinatein)/2-oxoglutarateout and glutamatein/aspartateout shuttles. Not all the exchange systems were reversible. The results support proposed schemes for metabolite transfer between glyoxysomes and mitochondria of castor bean endosperm during germination.

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PARTICIPATION OF THE GLYOXYLATE CYCLE IN THE METABOLISM OF ETHANOL BY CASTOR BEAN ENDOSPERM TISSUES

Canadian Journal of Biochemistry ◽

10.1139/o66-052 ◽

1966 ◽

Vol 44 (4) ◽

pp. 423-432 ◽

Cited By ~ 2

Author(s):

Carol A. Peterson ◽

E. A. Cossins

Keyword(s):

Castor Bean ◽

Tricarboxylic Acid Cycle ◽

Glyoxylate Cycle ◽

Experimental Period ◽

Tricarboxylic Acid ◽

Ethanol Metabolism ◽

Short Term ◽

Tissue Slices ◽

Acidic Amino Acids ◽

The Glyoxylate Cycle

The kinetics and pathway of ethanol metabolism in endosperm tissues of the germinating castor bean-have been studied by incubating tissue slices with micromolar quantities of ethanol-1-14C and ethanol-2-14C. In short term experiments, ethanol-14C was incorporated into the organic acids and acidic amino acids. When the experimental period was increased up to 1 hour, large amounts of ethanol-2-14C were incorporated into the sugars, and ethanol-1-14C was extensively incorporated into the respiratory carbon dioxide. Incorporation of ethanol-14C was stimulated by incubation of the tissues with glyoxylate. Ethanol metabolism was markedly inhibited by iodoacetate and malonate. These inhibitors also changed the distribution of14C in the products isolated. Isotopic competition studies indicated that ethanol was incorporated into the acids of the glyoxylate and the tricarboxylic acid cycles at rates substantially lower than acetate.The results are interpreted as being consistent with a metabolism of ethanol mainly via the glyoxylate cycle with some cycling of ethanol carbon through the tricarboxylic acid cycle.

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Faculty Opinions recommendation of Frataxin acts as an iron chaperone protein to modulate mitochondrial aconitase activity.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1020010.227455 ◽

2004 ◽

Author(s):

Dehua Pei

Keyword(s):

Aconitase Activity ◽

Chaperone Protein ◽

Mitochondrial Aconitase ◽

Iron Chaperone

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Co-ordinate regulation of genes involved in storage lipid mobilization in Arabidopsis thaliana

Biochemical Society Transactions ◽

10.1042/bst0290283 ◽

2001 ◽

Vol 29 (2) ◽

pp. 283-286 ◽

Cited By ~ 54

Author(s):

E. L. Rylott ◽

M. A. Hooks ◽

I. A. Graham

Keyword(s):

Arabidopsis Thaliana ◽

Enzyme Activities ◽

Phosphoenolpyruvate Carboxykinase ◽

Isocitrate Lyase ◽

Glyoxylate Cycle ◽

Molecular Genetic ◽

Regulation Of Gene Expression ◽

Growth Period ◽

Malate Synthase ◽

The Glyoxylate Cycle

Molecular genetic approaches in the model plant Arabidopsis thaliana (ColO) are shedding new light on the role and control of the pathways associated with the mobilization of lipid reserves during oilseed germination and post-germinative growth. Numerous independent studies have reported on the expression of individual genes encoding enzymes from the three major pathways: β-oxidation, the glyoxylate cycle and gluconeogenesis. However, a single comprehensive study of representative genes and enzymes from the different pathways in a single plant species has not been done. Here we present results from Arabidopsis that demonstrate the co-ordinate regulation of gene expression and enzyme activities for the acyl-CoA oxidase- and 3-ketoacyl-CoA thiolasemediated steps of β-oxidation, the isocitrate lyase and malate synthase steps of the glyoxylate cycle and the phosphoenolpyruvate carboxykinase step of gluconeogenesis. The mRNA abundance and enzyme activities increase to a peak at stage 2, 48 h after the onset of seed germination, and decline thereafter either to undetectable levels (for malate synthase and isocitrate lyase) or low basal levels (for the genes of β-oxidation and gluconeogenesis). The co-ordinate induction of all these genes at the onset of germination raises the possibility that a global regulatory mechanism operates to induce the expression of genes associated with the mobilization of storage reserves during the heterotrophic growth period.

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