Uricase: Localization in Hepatic Microbodies

Hruban, Z.; Swift, Hewson

doi:10.1126/science.146.3649.1316

Cited by 150 publications

(71 citation statements)

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“…These two enzymes have been found in microbodies isolated from many kinds of cells and are considered by de Duve to be distinctive enzymes of the class of microbodies named peroxisomes (11). Uricase is another enzyme which has been found in most of the peroxisome preparations so far described (4,22,(30)(31)(32)41). It is therefore of interest that, as shown in these investigations, uricase is also present in glyoxysomes.…”

Section: Methodsmentioning

confidence: 91%

Uricase and Allantoinase in Glyoxysomes

Theimer

Beevers

1971

Plant Physiol.

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In fat-degrading tissues of seedlings of seven different plant species examined, uricase activity (urate:02 oxidoreductase, EC 1.7.33) was associated with particulate fractions. After equilibrium density centrifugation on sucrose density gradients the enzyme activity was recovered in the glyoxysomal band (density: 1.25 grams per cubic centimeter). Allantoinase is also present in glyoxysomes but, equally, in the proplastid region (density: 1.22 grams per cubic centimeter). Xanthine oxidase, xanthine dehydrogenase, allantoicase, and urease were not detected in glyoxysomes from castor bean endosperm. Uricase in these particles shows its maximal activity at pH 8.9.The apparent Km is 7.4 AM. Urate concentrations greater than 120 MM as well as certain other purine compounds inhibit the enzyme. Cyanide at a concentration of 10 AM is a potent inhibitor. 2,6-Dichlorophenolindophenol did not substitute for oxygen as electron acceptor.The over-all reaction catalyzed by uricase (urate:02 oxidoreductase, EC 1.7.33) was elucidated by investigations with preparations from hog liver (27), fungi (15, 21), and bacteria (3). As shown in Figure 1, decarboxylation occurs at C-6, and the enzyme functions as an aerobic dehydrogenase. Highly purified preparations have been obtained from hog liver (28).Early cell fractionation studies with rat liver showed that urate oxidase sedimented with the crude mitochondrial fraction (38). Subsequently, by differential and equilibrium density centrifugation, the enzyme was shown to be associated with other oxidases that produce H202 (L-a-hydroxy acid oxidase, D-amino acid oxidase) and catalase in the class of microbody known as peroxisomes (4,11). Urate oxidase is in fact used as a marker enzyme for these organelles and has been shown to be present in peroxisomes from rat liver (11) and from liver and kidney of birds and amphibians (41) as well as in peroxisomes from certain protozoa (30)(31)(32) (44). In the present paper we describe properties of the enzyme from the endosperm of germinating castor bean seedlings and its subcellular localization in glyoxysomes from this and other fat-degrading tissues. MATERIALS AND METHODSPlant Material. Leaves from tobacco (Nicotiana tabacum) and corn (Zea mays) were cut from young plants grown in the greenhouse. Sunflower (Helianthus annuus), safflower (Carthamus tinctorius), and corn seeds were sterilized with 0.5% sodium hypochlorite (Clorox) solution for 20 min, soaked in distilled water for approximately 5 hr, and germinated on moist paper towels at 30 C in the dark for 5 to 6 days.Seeds of the one-leaved pinyon (Pinus monophylla) were collected in the Panamint Mountains (SW Death Valley) and of the Joshua tree at the Walker Pass (California). After sterilization with 10% Clorox solution for 20 min, the seeds were soaked for 8 to 10 hr in distilled water and germinated in moist vermiculite at 30 C and 90% relative humidity in the dark for 5 days (pinyon) or 9 days (Joshua tree). Seeds of castor bean (Ricinus communis) were germinated as described p...

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Section: Methodsmentioning

confidence: 91%

Uricase and Allantoinase in Glyoxysomes

Theimer

Beevers

1971

Plant Physiol.

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“…These criteria conform to published morphologic data for the identification of microbodies in rat liver (2)(3)(4)(5)(6)(7)(8)(9)15) . Furthermore, in all reacted material not a single normal-appearing, unstained microbody was observed, thus indirectly implying that the stained organelles must be the microbodies.…”

Section: Identification Of Microbodiesmentioning

confidence: 99%

“…The fine structure and enzyme content of the nucleoids of rat hepatic microbodies have been studied extensively (5,60,61) . Morphologically the nucleoids consist of parallel bundles of hollow tubules, which in cross-section have a honeycomb appearance and in longitudinal plane show a parallel packed, tubular structure (61) .…”

Section: The Relation Of the Reaction Product To The Nucleoids Of Micmentioning

confidence: 99%

“…Later Rouiller and coworkers (2, 3) described a somewhat similar structure in the rat liver, which was also designated as microbody and which in addition contained an electronopaque crystalloid core . Since then, numerous fine structural studies on hepatic microbodies of normal rats (4,5), rats with hepatoma (6, 7), and rats treated with different chemical agents have been published (8,9) .…”

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Cytochemical Localization of Peroxidatic Activity of Catalase in Rat Hepatic Microbodies (Peroxisomes)

Fahimi¹

1969

The Journal of Cell Biology

275

104

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Prominent staining of rat hepatic microbodies was obtained by incubating sections of aldehyde-fixed rat liver in a modified Graham and Karnovsky's medium for ultrastructural demonstration of peroxidase activity . The electron-opaque reaction product was deposited uniformly over the matrix of the microbodies . The microbodies were identified by their size, shape, presence of tubular nucleoids, and other morphologic characteristics, and by their relative numerical counts . The staining reaction was inhibited by the catalase inhibitor, aminotriazole, and by KCN, azide, high concentrations of H202, and by boiling of sections . These inhibition studies suggest that the peroxidatic activity of microbody catalase is responsible for the staining reaction . In the absence of exogenous H202 appreciable staining of microbodies was noted only after prolonged incubation .

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“…The most conspicuous structural component of the peroxisome is a dense core, which has been described as crystalline, semicrystalline, crystalloid, or maltilamellated, mostly on the basis of electron microscopic images and is made up of regular striation with a honeycomb appearance (2). Biochemical analyses showed that the structure was made of urate oxidase (4,5). Peroxisome deficiencies participate in a variety of pathologies, including Zellweger syndrome.…”

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confidence: 99%

Peroxisome degradation in mammals

2011

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SummaryThis review summarizes the historical aspects of the study of peroxisome degradation in mammalian cells. Peroxisomes have diverse metabolic roles in response to environmental changes and are degraded in a preferential manner, by comparison with cytosolic proteins. This review introduces three hypotheses on the degradation mechanisms: (a) the action of the peroxisomespecific Lon protease; (b) the membrane disruption effect of 15-lipoxygenase; and (c) autophagy that sequesters and degrades the organelles by lysosomal enzymes. Among these hypotheses, autophagy is now recognized as the most important mechanism for excess peroxisome degradation. One of the most striking characteristics of peroxisomes is that they are markedly proliferated in the liver by the administration of hypolipidemic drugs and industrial plasticizers. The effects of these substances were fully reversed after withdrawal of the substances, and most of the excess peroxisomes were selectively degraded and recovered to a normal number and size. Autophagic degradation of peroxisomes has been examined using this characteristic phenomenon. Excessive peroxisome degradation that occurs after cessation of hypolipidemic drugs has been extensively investigated biochemically and morphologically. The evidence shows that the degradation of excess peroxisomes and peroxisomal enzymes is inhibited by 3-methyladenine (3-MA), a specific inhibitor of autophagy. Furthermore, in liver-specific autophagy-deficient mice, rapid removal of peroxisomes was exclusively impaired, and degradation of peroxisomal enzymes was not detected. Thus, the significant contribution of autophagic machinery to peroxisomal degradation in mammals was confirmed. However, the important question of the mechanism for the selective recognition of peroxisomes by autophagosomes remains to be fully elucidated.

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Uricase: Localization in Hepatic Microbodies

Abstract: Microbodies of rat hepatic cells and hepatomas contain a crystalloid with the same structural characteristics as crystals of purified uricase, when viewed by electron microscopy. We conclude that crystalline uricase is located within hepatic microbodies.

Cited by 150 publications

References 7 publications

Uricase and Allantoinase in Glyoxysomes

Uricase and Allantoinase in Glyoxysomes

Cytochemical Localization of Peroxidatic Activity of Catalase in Rat Hepatic Microbodies (Peroxisomes)

Peroxisome degradation in mammals

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