A protein drp90 encoded on the leftwards strand of soybean nodule urate oxidase cDNA binds to a regulatory sequence in leghemoglobin C3 gene.
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Rasburicase has been defined as a potent urolytic agent for management of malignancy-associated hyperuricemia. We reviewed the data of 26 children with malignancy at risk for TLS who received rasburicase for treatment or prophylaxis of acute hyperuricemia, producing a significant decrease in uric acid level in all the patients. Tolerance of treatment was excellent. Rasburicase is a safe, highly and rapidly effective agent in the treatment and prevention of malignancies-associated acute hyperuricemia.
A highly purified uratoxidase was isolated from the pig liver. The sedimentation coefficient of the enzyme was 6.96 S and the molecular weight was 122,000 +/- 4,000. The enzyme was a tetramer consisting of subunits with a molecular weight of 31,600 +/- 2,500. Uratoxidase showed high substrate specificity with 0.05 M borate buffer, pH 8.5. During competitive inhibition 8-azaxanthine (Ki = 3.1 X 10(-7) M) produced the strongest inhibitory effect as compared with other purine compounds. N-chloromercuric benzoate and ascorbic acid also inhibited strongly uratoxidase activity. EDTA-Na2, methyl ester of n-oxybenzoic acid, phenyl methyl sulphonyl fluoride and cystein did not influence the enzyme activity.
Anurate oxidase (uricase, EC 1.7.3.3) gene from Candida utilis AS2.117 was cloned by PCR amplification with primers derived from conserved regions of published uicase DNA sequence. The DNA sequence of cloned uricase gene was determined and a high homology compared to the reported gene was found. The cloned gene was inserted into Bam H I and Nde I sites of pET21a to create the recombinant plasmid pURO. In Escherichia coli BL21(DE3) host, the expression lever of uricase reached to about 40% of total soluble proteins of the cell. The western blot analysis confirmed the result of expression. Properties of the enzyme protein produced by E. coli BL21(DE3)/pURO were determined and similar with those of original protein from Candida utilis AS2.117. Furthermore, the thermostability of the expressed protein was enhanced. The purified recombinant uricase was used in serum uric acid analysis.
The biogenesis of peroxisomes has been investigated in the model of regenerating rat liver after partial hepatectomy using ultrastructural cytochemical staining methods: catalase as a marker of the peroxisomal matrix and uricase for the cores. The peroxisomes in regenerating rat liver showed several distinctive features: a) marked variation in shape and size, e.g., peroxisomes with tail-like extensions and tortuously elongated rod-shaped ones, b) formation of peroxisomal clusters and, c) interconnections between adjacent peroxisomes suggesting cleavage or budding. Whereas the reaction product for catalase was present at all intervals after hepatectomy in the matrix of all peroxisomes, the pattern of localization of uricase case varied with the time. It was confined to the cores in controls and at 10 days after the operation, while at 24 and 48 h it showed, in addition, a diffuse reaction in the matrix of some peroxisomes. In interconnected apparently dividing peroxisomes, the core with positive uricase reaction was present only in one half, while the other half was devoid of the reaction product. Similarly, the diffuse uricase staining was confined to the half which contained the core with the other half remaining unstained. These observations are consistent with the concept that new peroxisomes are formed from preexisting ones by budding and segmentation. While catalase is transferred uniformly to all new segments, uricase is compartmentalized in certain portions, of the apparently growing "peroxisomal reticulum".
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The effect of suloctidil (120 mg/kg body weight PO for 3 weeks) on rat liver was investigated using biochemical and morphological methods: enzymatic activities characteristic of the main cellular compartments were used as biochemical markers of hepatocyte function and morphometry was applied to investigate morphological changes. No sign of hepatotoxicity was evidenced after suloctidil treatment (liver weight; cytochrome c oxidase; glucose 6-phosphatase; NADPH-cytochrome c reductase; D-amino acid oxidase; urate oxidase; fatty acid oxidation; peroxisomal number, volume and size distribution). Suloctidil increased catalase activity by 22% without morphologically detectable changes in the peroxisomes. After suloctidil treatment, slightly increased mitochondrial volume fraction and slightly decreased mitochondrial number were noted without significant changes in cytochrome c oxidase. Clofibrate, at the same dose, increased NADPH-cytochrome c reductase, catalase, acylCoA oxidase, mitochondrial and peroxisomal number and volume fraction, and decreased urate oxidase activity.
Urate oxidase, or uricase (EC 1.7.3.3), is a purine metabolic enzyme that catalyzes the conversion of uric acid to allantoin in most mammals except humans and certain other primates. The loss of urate oxidase in the human during primate evolution predisposes man to hyperuricemia, a metabolic disturbance that can lead to gouty arthritis and renal stones. To create a mouse model for hyperuricemia and gout, and to address the question of whether urate oxidase is essential in lower mammalian species, we have disrupted the urate oxidase gene in the mouse by homologous recombination in embryonic stem cells. Unlike the human situation, urate oxidase deficiency in mice causes pronounced hyperuricemia and urate nephropathy. More than half of the mutant mice died before 4 weeks of age, indicating that urate oxidase is essential in mice. These mutant mice may also serve as animal models for hyperuricemia and its related nephropathy in humans.
The effect of thyroid hormone on peroxisomal enzyme activity was studied in thyroidectomized- and T4-administered-thyroidectomized rats. In liver, the activities of isozyme A of L-alpha-hydroxyacid oxidase, D-amino acid oxidase, urate oxidase and catalase were decreased by thyroidectomy, and the diminished enzyme activities were restored by T4 administration to rats. These modifications induced by thyroidectomy or by T4 administration, however, were prominent only in immature animals (20-day-old rats). Although the changes in-alpha-hydroxyacid oxidase and D-amino acid oxidase activities, induced by thyroidectomy or by T4 administration, were also observed in 40-day-old rats, those in urate oxidase and catalase activities were not significant in 40-day-old rats. Acyl CoA oxidase activity was not affected by thyroidectomy or by T4 administration in either 20- or 40-day-old rats. In the kidney, isozyme B of L-alpha-hydroxyacid oxidase activity was reduced by thyroidectomy and the diminished enzyme activity was restored by T4 administration in both 20- and 40-day-old rats. D-Amino acid oxidase and catalase activities in kidney, however, were not significantly modified by thyroidectomy or by T4 administration in either 20- or 40-day-old rats. The results suggest that thyroid hormone can modify the peroxisomal enzyme activity, which is prominent in immature animals.
The distribution of catalase, amino acid oxidase, alpha-hydroxy acid oxidase, urate oxidase and alcohol oxidase was studied cytochemically in rat hepatocytes. The presence of catalase was demonstrated with the conventional diaminobenzidine technique. Oxidase activities were visualized with methods based on the enzymatic or chemical trapping of the hydrogen peroxide produced by these enzymes during aerobic incubations. All enzymes investigated were found to be present in peroxisomes. Catalase activity was found in the peroxisomal matrix, but also associated with the nucleoid. After staining for oxidase activities the stain deposits occurred invariably in the peroxisomal matrix as well as in the nucleoids. In all experiments the activity of both catalase and the oxidases was confined to the peroxisomes. The presence of a hydrogen peroxide-producing alcohol oxidase was demonstrated for the first time in peroxisomes in liver cells. The results imply that the enzyme activity of the nucleoids of rat liver peroxisomes is not exclusively due to urate oxidase. The nucleoids obviously contain a variety of other enzymes that may be more or less loosely associated with the insoluble components of these structures.
1. Liver catalase, D-amino acid oxidase, urate oxidase of Alytes obstetricans and Xenopus laevis (anuran amphibians) and fatty acyl-CoA oxidase of Alytes were present at all post-embryonic stages. 2. Catalase and D-amino acid oxidase activities increased during spontaneous metamorphosis of the two species. 3. During triiodothyronine-induced metamorphosis of Alytes larvae, catalase and D-amino acid oxidase activities increased after a latent period. 4. Our results suggest that expression of some hepatic peroxisomal enzymes is modulated by thyroid hormones.
RMI 14, 514 ([5-tetradecycloxy]-2-furancarboxylic acid) represents a new class of hypolipidemic agents which cause unusual ultrastructural changes in liver of male rats and in selected peroxisomal enzymes in liver and kidney of both sexes. Among the principal ultrastructural changes in peroxisomes of male rat liver were (a) cavitation and compartmentalization of the matrix, often giving the appearance of a peroxisome-within-a-peroxisome, and (b) narrow, dense extensions of canaliculi or cisterns from the periphery of the peroxisome, forming partial circlets or surrounding irregular areas of cytoplasm. The unusual enzyme responses were (a) elevation of catalase activity in liver and kidney in female rats, (b) increased activity of three hydrogen peroxide-producing oxidases (urate oxidase, L-alpha-hydroxy acid oxidase, and D-amino acid oxidase) in the liver of both sexes, and (c) elevation of activity of the last two oxidases in male kidney. The peculiar ultrastructural changes in liver peroxisomes combined with the responses of selected peroxisomal enzymes represent unusual modulations or adaptations of these organelles to a hypolipidemic agent, the effects of which have not been reported extensively.
This study attempts to clarify peroxisomal enzyme activity changes in the atrophying tail of anuran tadpoles. Changes in catalase, D-amino acid oxidase and urate oxidase activity were spectrophotometrically investigated using tadpole tails of Rana japonica and Rana nigromaculata. In R. japonica, total catalase activity decreased in tails undergoing regression during spontaneous and DL-thyroxine (T4)-induced metamorphosis, whereas total D-amino acid oxidase and urate oxidase activity increased. In R. nigromaculata, total activity of catalase decreased in tails regressing spontaneously. Total D-amino acid oxidase activity increased during advanced stages of tail regression, but total urate oxidase activity decreased. Specific activity of tadpole peroxisomal enzymes in the above two species was found to be highest for D-amino acid oxidase, followed by urate oxidase and then catalase at latter stages of normal tail regression. Atrophying tadpole tails develop a mechanism for hydrogen peroxide production, which may contribute to cell death in this organ.
After administration of a hypolipidemic drug, MLM-160, to male rats, liver peroxisomes were studied by biochemical, cytochemical, and immunocytochemical methods. The activities of D-amino acid oxidase, glycolate oxidase, and urate oxidase increased 2 to 3-fold by the treatment. The increase of the oxidases was confirmed by immunoblotting analysis. By light microscopy, immunoreaction for catalase was present in the cytoplasmic granules of hepatocytes. The stained granules formed some clusters and overlapped each other after MLM-160 treatment. However, immunostaining for D-amino acid oxidase and urate oxidase was present in discrete fine granules which did not overlap each other. By electron microscopy, many peroxisomes showed ring-like extensions and cavitation of the matrix, often giving the appearance of a peroxisome-within-a-peroxisome. In many cases, these unusual peroxisomes seemed to be interconnected with each other. Within the peroxisomes, the catalase was localized in the matrix. Urate oxidase was associated with the crystalloid cores. D-amino acid oxidase was localized focally in a small part of the matrix where the catalase was mostly negative. In conclusion, the administration of MLM-160 to male rats induces some peroxisomal oxidases, accompanying the appearance of unusual peroxisomes. The precise localization of peroxisomal enzymes suggested that there are subcompartments within the liver peroxisomes as shown in rat kidney peroxisomes.