Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This research investigated transport of bovine milk xanthine oxidase into mammary glands of the lactating rat. Transport capability suggested an exogenous, nonmammary, source for the enzyme. Five lactating rats were injected intracardially with 100 microgram of purified iodine-125 labeled xanthine oxidase and five were injected with 100 microgram of the enzyme unpurified. Four hours later the rodents were hand-milked, and radiation was confirmed in all samples by liquid scintillation counting. Counts were recorded per volume of milk and the percentage radiation was computed. Autoradiographs of the rats indicated radiation almost exclusively associated with the mammary glands. Greatest concentration of radioactivity was in the micellar casein fraction of milk, and a compound of high molecular weight, presumably [iodine-125]xanthine oxidase, was confirmed by gel filtration of the casein. Results suggest that the compound was transported into the mammary glands. The degree of transport was dependent upon the stage of lactation.
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PMID:Transport of bovine milk xanthine oxidase into mammary glands of the rat. 64 Dec 39

Methodological difficulties have been encountered when proteases were omitted from the conventional isolation of bovine milk xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2). The use of these conventional methods has been studied and modified to reduce the problems encountered. Some of the difficulties may be due to the presence of high concentrations of caseins, which exhibit a wide range of charges and sizes, thereby making separations based on charge and size more complicated. In addition, non-covalent interactions may occur between the caseins and xanthine oxidase leading to the formation of casein-xanthine oxidase micellar aggregates. The difficulties encountered in this conventional isolation have been circumvented by purifying the enzyme directly from milk fat globule membranes that first have been washed free of most casein and other milk proteins. The xanthine oxidase is isolated by ultrafiltration through an Amicon XM-100A membrane at 5 degrees C in 0.25 M sucrose/5 mM sodium salicylate. The largest molecular size of globular proteins which can penetrate this ultrafiltration membrane has been previously estimated to be around 100 000 daltons. Xanthine oxidase thus appears to be smaller than 100 000 daltons in its native state. The size observed for active xanthine oxidase previously isolated by other methods has been around 275 000--300 000 daltons. Xanthine oxidase isolated by ultrafiltration appears similar to xanthine oxidase from conventional isolation methods according to empirical criteria of homogeneity based on size and also on the absorbances at 280 and 450 nm. Criteria based on charge were found to be less reliable.
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PMID:Bovine milk xanthine oxidase: purification by ultrafiltration and conventional methods which omit addition of proteases: some criteria for homogeneity of native xanthine oxidase. 71 40

Rats were fed a 5 or 20% casein diet that causes liver necrosis unless supplemented with vitamin E or selenite. The following activities were studied in liver subcellar fractions: enzymic formation of lipid peroxides, NADPH-cytochrome c reductase, oxidative demethylation of aminopyrine, and incorporation of [14C]leucine into protein (with microsomes); xanthine oxidase (with soluble supernatant); and RNA polymerases I and II (with nuclei). Formation of lipid peroxides was higher in rats fed diets without vitamin E and was not reduced significantly by dietary selenite. The activity of xanthine oxidase was higher in animals fed the 20% casein than in those fed the 5% casein diet; however, a higher activity was observed in the rats fed the latter diet without vitamin E or selenite than in those receiving these supplements. The activity of RNA polymerase I was higher in rats fed the low casein diet. Other activities examined were not affected significantly by the level of dietary casein or by vitamin E or selenits.
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PMID:Studies on the formation of lipid peroxides and on some enzymic activities in the liver of vitamin E-deficient rats. 111 48

Protein restriction ameliorates proteinuria in acute adriamycin (ADR) nephrosis and decreases the renal levels of xanthine oxidase (XO), a putative mediator of ADR nephrotoxicity. Hypothetically, the effect of protein restriction on renal XO levels may be due to variations in plasma and tissue proteic amino acids (AA). To elucidate this point, the levels of AA in plasma and in renal homogenates were determined in rats with ADR nephrosis and fed diets with different protein contents: (a) high (35%) casein; (b) standard (21%) casein; (c) low (9%) casein; (d) low casein plus a synthetic mixture of Val, Leu and Ile. The protein content of the diet determined certain marked variations in plasma AA: high levels of Val, Leu and Ile were found in rats fed on a high protein diet, while the same AA were low, in rats on low protein regimen. Supplementation of the low protein diet with a synthetic mixture of branched-chain AA (Val, Leu and Ile) normalized the plasma levels of these AA. In spite of these changes, tissue AA were similar in all groups, regardless of the protein contents of the diets. Furthermore, the levels of renal XO and proteinuria were unrelated to variations in plasma AA, since both parameters were low in protein-restricted and protein-restricted AA-supplemented rats while high in rats fed a high or normoproteic diet. These data demonstrate that low protein diets induce marked alterations in plasma AA composition which are similar in may respects to those found in protein malnutrition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Modulation of proteinuria and renal xanthine oxidase activity by dietary proteins in acute adriamycin nephrosis in rats: lack of correlation with intra- and extracellular amino acids. 156 88

1. Nilvadipine (FK 235, FR 34235) suppressed ischemia (20 min)-reflow (20 min)-induced paw edema of mice (ED30:0.4 mg/kg i.v. and 2 mg/kg p.o.). Other calcium entry blockers of dihydropyridine-type also suppressed the edema, but 30-fold higher doses were required. 2. Oral dosing of nilvadipine suppressed carrageenan-induced paw edema (ED30:15 mg/kg in rats and 20 mg/kg in mice) at a potency corresponding to that of an anti-inflammatory drug, ibuprofen. Nifedipine, nicardipine and nimodipine resulted in a suppression of 30% only with 100 mg/kg oral dosing in rats. Nitrendipine, diltiazem and verapamil were without effect. 3. Nilvadipine inhibited superoxide radical (O-2production from xanthine oxidase (XOD) both with lactate dehydrogenase + NADH method and cytochrome c method (IC50:90 and 100 micrograms/ml, respectively). Nifedipine and nicardipine showed some inhibition, but the other calcium entry blockers failed to inhibit significantly even at 320 micrograms/ml. As uric acid formation was not reduced by the tested drugs, the inhibitory action might be due to their O-2scavenging effects. 4. Superoxide production of neutrophils from casein-induced peritoneal fluid in rats was most strongly inhibited by nilvadipine when the cells were stimulated by a calcium ionophore, A23187 (IC50:4 micrograms/ml). Inhibition by this drug when stimulated by f-methonyl-leucyl-phenylalanine and phorbol myristate acetate was less effective (IC50:20 and 30 micrograms/ml, respectively). Nifedipine and nicardipine inhibited neutrophil O-2production at higher concentrations (30-200 micrograms/ml) with all stimulants. Inhibitory actions by other drugs were weak. 5. Triggering of atherosclerosis depends largely on the oxidative stress on blood vessels after recently established concept.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition by nilvadipine of ischemic and carrageenan paw edema as well as of superoxide radical production from neutrophils and xanthine oxidase. 165 7

Xanthine oxidase, isolated from bovine milk, exhibited an A280:A450 nm ratio of 5.0. This ratio is reported to be indicative of highly purified enzyme preparations. Serum from a rabbit hyperimmunized against this enzyme fraction exhibited two precipitation lines when incubated with the protein in agarose double diffusion plates. Serum albumin, beta-lactoglobulin, alpha-lactalbumin, lactoferrin, casein, chymosin, and immunoglobulin were tested for reactivity. The second antigen was identified as bovine immunoglobulin. Commercial preparations of xanthine oxidase also contained immunoglobulin as a contaminant. IgG and IgA were present in Sigma (Grade III) fractions and IgM was identified in Boehringer Mannheim preparations. Immunofluorescent studies indicated that xanthine oxidase antiserum reacted with the capillary endothelium of bovine heart. Absorption of this antiserum with bovine IgG abrogated this reaction. These findings may explain apparent discrepancies between reported immunohistological association of xanthine oxidase in heart capillary endothelial cells and the absence of detectable enzymatic activity.
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PMID:Copurification of bovine milk xanthine oxidase and immunoglobulin. 191 Feb 86

Proteinuria and renal xanthine metabolising enzymes, xanthine oxidase and xanthine dehydrogenase, were evaluated in Adriamycin-treated rats fed standard (21% casein) and low-protein (6% casein) diets. In rats fed a standard diet Adriamycin was associated with increased activities in the kidney of xanthine oxidase and xanthine dehydrogenase and induced massive proteinuria. The pharmacological block of both enzymes by allopurinol and tungsten block of both enzymes by allopurinol and tungsten reduced proteinuria to one-third of the original levels. Rats fed a low-protein diet presented decreased levels of renal xanthine oxidase and xanthine dehydrogenase and were only slightly proteinuric. Finally, rats shifted from a low-protein diet to a normal one developed massive proteinuria in spite of normal or slightly decreased levels of renal xanthine oxidase and xanthine dehydrogenase. We conclude that a low-protein diet is effective in decreasing the levels of xanthine metabolising enzymes that are in part responsible for the renal damage due to Adriamycin. This is not however the unique mechanism by which the low-protein diet protects against the development of proteinuria in Adriamycin nephrosis; other factors must also be hypothesised.
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PMID:Low-protein diet and xanthine-metabolising enzymes in adriamycin nephrosis. 212 63

1. A low protein diet prevents the development of proteinuria and glomerular damage in adriamycin experimental nephrosis without affecting renal haemodynamics. In this study the hypothesis was tested as to whether protein restriction is able to modulate the purine metabolic cycle and related enzymes such as xanthine oxidase, one of the putative effectors of adriamycin nephrotoxicity. 2. Renal activities of xanthine oxidase and purine nucleoside phosphorylase were markedly depressed in adriamycin-treated rats fed a 9% casein (low protein) diet compared with the group fed a 22% casein (normal protein) diet both 1 day after adriamycin administration and at the time of appearance of heavy proteinuria (day 15), whereas the activity of renal adenosine deaminase was unchanged. 3. The concentrations of the metabolic substrates of xanthine oxidase, i.e. hypoxanthine and xanthine, were constantly lower in renal homogenates of rats fed a low protein diet compared with those on a normal protein diet. In urine, uric acid, the product of hypoxanthine-xanthine transformation, was lower 1 day after adriamycin injection in protein-restricted rats compared with the group on a normal protein diet which showed a marked increase in its excretion. At the same time, the urinary efflux of adenosine 5'-monophosphate, which is the precursor nucleotide of the above-mentioned nucleosides and bases, was very high in rats fed a low protein diet, whereas it was absent in the group on a normal protein diet. 4. The progressive increment in proteinuria of glomerular origin (i.e. increased excretion of albumin and transferrin) typical of adriamycin-treated rats fed a normal protein diet was inhibited in the protein-restricted animals, which were normoproteinuric on day 10 and were only slightly proteinuric on day 15. 5. Like protein restriction, the pharmacological suppression of renal xanthine oxidase by dietary tungstate and the scavenging by dimethylthiourea of the putative free radical deriving from the action of xanthine oxidase, were associated with a similar (quantitative and qualitative) inhibition of glomerular proteinuria. 6. These data demonstrate that dietary protein restriction is associated with a block in purine metabolism within the kidney due to a marked reduction in the activities of two main enzymes of the cycle, i.e. purine nucleoside phosphorylase and xanthine oxidase, the latter being a putative effector of adriamycin nephrotoxicity. The partial reduction of proteinuria induced by a low protein diet is quantitatively and qualitatively comparable with the reduction induced by the specific block of renal xanthine oxidase or by the scavenging of OH.deriving from hypoxanthine and xanthine transformation.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of dietary protein restriction on renal purines and purine-metabolizing enzymes in adriamycin nephrosis in rats: a mechanism for protection against acute proteinuria involving xanthine oxidase inhibition. 217 53

The presence of antibodies of the IgA class against dietary antigens (bovine IgG (BGG), beta-lactoglobulin, casein, alpha-lactalbumin and xanthine oxidase, chicken ovalbumin and crude gliadin) was checked in the sera of 23 severely atherosclerotic subjects (ATS) and 20 highly selected controls (C). In these subjects an association between serum IgA levels and atherosclerosis had previously been shown. Determinations were performed by a micro-ELISA method and results were expressed as absorbances at 405 nm x 1000. Higher levels of IgA antibodies were found in ATS with respect to C against beta-lactoglobulin (respectively, 113.4 +/- 152.4 (1 SD) vs. 40.0 +/- 34.2; P less than 0.005) and casein (69.8 +/- 35.5 vs. 52.4 +/- 27.5; P less than 0.05). There was no difference in IgG and IgM against these 2 proteins between the 2 groups. Significant differences of prevalence of IgA antibodies were found for the following antigens: beta-lactoglobulin (4 C and 16 ATS over the limit value of 51; P less than 0.002), xanthine oxidase (1 C and 9 ATS over 289; P less than 0.01), BGG (7 C and 17 ATS over 87; P less than 0.02) and casein (5 C and 14 ATS over 60; P less than 0.02). These data suggest an association between anti-milk IgA antibodies and atherosclerosis. Its relevance and significance deserves further investigation.
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PMID:Association of serum IgA antibodies to milk antigens with severe atherosclerosis. 275 57

When exposed to oxidative stress, by oxygen radicals or H2O2, E. coli exhibited decreased growth, decreased protein synthesis, and dose-dependent increases in protein degradation. The quinone menadione induced proteolysis when cells were incubated in air, but was not effective when cells were incubated without oxygen. Anaerobically grown cells also exhibited significantly lower proteolytic capacity than did cells that were grown aerobically. Xanthine plus xanthine oxidase (which generate O2- and H2O2) caused a stimulation of proteolysis which was inhibitable by catalase, but not by superoxide dismutase: Indicating that H2O2 was responsible for the increased protein degradation. Indeed, H2O2 alone was effective in inducing increased intracellular proteolysis. Two-dimensional polyacrylamide gel electrophoresis of [3H]leucine labeled E. coli revealed greater than 50% decreases in the concentrations of 10-15 cell proteins following H2O2 or menadione exposure, while several other proteins were less severely affected. To test for the presence of soluble proteases, we prepared cell-free extracts of E. coli and incubated them with radio-labeled protein substrates. E. coli extracts degraded casein and globin polypeptides at rapid rates but showed little activity with native proteins such as superoxide dismutase, hemoglobin, bovine serum albumin, or catalase. When these same proteins were denatured by exposure to oxygen radicals or H2O2, however, they became excellent substrates for degradation in E. coli extracts. Studies with albumin revealed correlations greater than 0.95 between the degree of oxidative denaturation and proteolytic susceptibility. Pretreatment of E. coli with menadione or H2O2 did not increase the proteolytic capacity of cell extracts; indicating that neither protease activation, nor protease induction were required.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Degradation of oxidatively denatured proteins in Escherichia coli. 290 82


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