Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

High activity alkaline protease was obtained when the enzyme was immobilized on Dowex MWA-1 (mesh 20-50) with 10% glutaraldehyde in chilled phosphate buffer (M/15, PH 6.5). Activity yields of the protease and rennet were 27 and 29, respectively. The highest activities appeared at 60 degrees C, pH 10 for alkaline protease and 50 degrees C, pH 4.0 for rennet. The properties of both proteases were not essentially changed by the immobilization except that the Km values of both enzymes were increased about tenfold as a result of immobilization. Both proteases in the immobilized state were more stable than those in the free state at 60 degrees C. Other peptide hydrolases, beta-galactosidase, invertase, and glucoamylase, were successfully immobilized with high activities, but lipase, hexokinase, glucose-6-phosphate dehydrogenase, and xanthine oxidase became inactive.
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PMID:Preparation and properties of proteases immobilized on anion exchange resin with glutaraldehyde. 2 75

Crude cell-free extracts of nine strains of Streptomyces tested for nitroalkane-oxidizing activity showed production of nitrous acid from 2-nitropropane, 1-nitropropane, nitroethane, nitromethane, and 3-nitropropionic acid. These substrates were utilized in most strains but to a decreasing extent in the order given, and different strains varied in their relative efficiency of oxidation. p-Nitrobenzoic acid, p-aminobenzoic acid, enteromycin, and omega-nitro-l-arginine were not attacked. d-Amino acid oxidase, glucose oxidase, glutathione S-transferase, and xanthine oxidase, enzymes potentially responsible for the observed oxidations in crude cellfree extracts, were present at concentrations too low to play any significant role. A nitroalkane-oxidizing enzyme from streptozotocin-producing Streptomyces achromogenes subsp. streptozoticus was partially purified and characterized. It catalyzes the oxidative denitrification of 2-nitropropane as follows: 2CH(3)CH(NO(2))CH(3) + O(2) --> 2CH(3)COCH(3) + 2HNO(2). At the optimum pH of 7.5 of the enzyme, 2-nitropropane was as good a substrate as its sodium salt; t-nitrobutane was not a substrate. Whereas Tiron, oxine, and nitroxyl radical acted as potent inhibitors of this enzyme, superoxide dismutase was essentially without effect. Sodium peroxide abolished a lag phase in the progress curve of the enzyme and afforded stimulation, whereas sodium superoxide did not affect the reaction. Reducing agents, such as glutathione, reduced nicotinamide adenine dinucleotide, and nicotinamide adenine dinucleotide phosphate, reduced form, as well as thiol compounds, were strongly inhibitory, but cyanide had no effect. The S. achromogenes enzyme at the present stage of purification is similar in many respects to the enzyme 2-nitropropane dioxygenase from Hansenula mrakii. The possible involvement of the nitroalkane-oxidizing enzyme in the biosynthesis of antibiotics that contain a nitrogen-nitrogen bond is discussed.
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PMID:Nitroalkane oxidation by streptomycetes. 3 65

The degradation of DNA by bleomycin was studied in the absence and in the presence of added reducing agents, including 2-mercaptoethanol, dithiothreitol, reduced nicotinamide adenine dinucleotide phosphate, H2O2, and ascorbate, and in the presence of a superoxide anion generating system consisting of xanthine oxidase and hypoxanthine. In all cases, breakage of DNA was inhibited by low concentrations of chelators; where examined in detail, deferoxamine mesylate was considerably more potent than (ethylenedinitrilo)tetraacetic acid. Iron was found to be present in significant quantities in all reaction mixtures. Thus, the pattern of inhibition observed is attributed to the involvement of contaminating iron in the degradation of DNA by bleomycin. Cu(II), Zn(II), and Co(II) inhibit degradation of DNA by bleomycin and Fe(II) in the absence of added reducing agents. A model is proposed in which the degradation of DNA in these systems is dependent on the oxidation of an Fe(II)-bleomycin-DNA complex.
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PMID:Effect of chelating agents and metal ions on the degradation of DNA by bleomycin. 8 Feb 26

The presence of anions of phosphate (Pi), pyrophosphate (PPi), adenine nucleotides and sulfate greatly enhanced the production of superoxide radical (-O-2) by isolated guinea-pig macrophages. These anions, however, failed to enhance the production of -O-2 by the xanthine oxidase system, suggesting that they serve only as activators of -O-2 generating enzyme(s) located on the macrophage cell membrane. Many other common anions were ineffective in the macrophage system. In the presence of concentrations of Pi, PPi, adenine-5'-triphosphate (ATP) reported to be in the synovial fluid, -O-2 was produced efficiently and was inhibited by diclofenac sodium. These anions induced rat paw edema, maintained the swelling at least up to 6 h. The edema was suppressed partially by repeated injection of superoxide dismutase (SOD). High doses of sodium chloride and nitrate failed to maintain the swelling.
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PMID:Role of phosphate, pyrophosphate, adenine nucleotides and sulfate in activating production of the superoxide radical by macrophages, and in formation of rat paw edema. 19 85

Chromatophores prepared from Chromatium exhibit a light-dependent O2 uptake in the presence of reduced 2,6-dichlorophenolindophenol, the maximum rate observed being 10.8 micronmol (mg of Bchl)-1 h-1 (air-saturated condition). As it was found that the uptake of O2 was markedly inhibited by superoxide dismutase, it is suggested that molecular oxygen is subject to light-dependent monovalent reduction, resulting in the formation of the superoxide anion radical (O2-). By coupling baker's yeast transketolase with illuminated chromatophore preparations, it was demonstrated that [U-14C]-fructose 6-phosphate (6-P) is oxidatively split to produce glycolate, and that the reaction was markedly inhibited by superoxide dismutase and less strongly by catalase. A coupled system containing yeast transketolase and xanthine plus xanthine oxidase showed a similar oxidative formation of glycolate from [U-14C] fructose 6-P. It is thus suggested that photogenerated O2- serves as an oxidant in the transketolase-catalyzed formation of glycolate from the alpha, beta-dihydroxyethyl (C2) thiamine pyrophosphate complex, whereas H2O2 is not an efficient oxidant. The rate of glycolate formation in vitro utilizing O2- does not account for the in vivo rate of glycolate photosynthesis in Chromatium cells exposed to an O2 atmosphere (10 micronmol (mg of Bchl)-1 h-1). However, the enhancement of glycolate formation by the autoxidizable electron acceptor methyl viologen in Chromatium cells in O2, as well as the strong suppression by 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron), an O2- scavenger, suggest that O2- is involved in the light-dependent formation of glycolate in vivo.
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PMID:Enzymic formation of glycolate in Chromatium. Role of superoxide radical in a transketolase-type mechanism. 19 57

Two types of complexes are formed during the interaction of xanthine oxidase with p-chloromercurybenzoate (pCMB). The reversible inactive complex (presumably of absorption nature) is formed practically instantaneously and competitively with regard to the substrate (Ki=6,2 . 10(-8) M) in 0,05 M phosphate buffer (pH 7,8, 25 degrees) and does not involve the fast-reacting SH-groups of the enzyme. Reactivation of xanthine oxidase is observed during prolonged incubation of the inactive complex at 0 degrees; it is associated with the interaction between pCMB and the fact-reacting SH-groups. This interaction results in a dissociation of the inactive complex. The blocking of the slow-reacting SH-groups is accompanied by an irreversible loss of the xanthine oxidase activity. The enzyme modification by blocking of 10 fast-reacting SH-groups does not involve the Fe-S clusters, but results in local changes in the enzyme conformation. This is manifested in a 2-fold increase of Km and the rate constants of proteolysis of the modified xanthine oxidase as compared to the native enzyme. The rate constants of proteolysis by trypsin for the native and modified enzymes in 0,05 M phosphate buffer (pH 7,8; 37 degrees) are 3,7 . 10(-3) min-1 and 7,0 . 10(-3) min-1, respectively; those for chymotrypsin in the same buffer (30 degrees) are 1,5 . 10(-2) min-1 and 6,0 . 10(-2) min-1, respectively.
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PMID:[Mechanism of interaction between milk xanthine oxidase and p-chloromercuribenzoate. Properties of the purified enzyme]. 49 85

Six female and four male albino guinea pigs were immunized with active purified xanthine oxidase of bovine milk mixed with equal volume of Freund's complete adjuvant. One male and one female were immunized with heat-inactivated xanthine oxidase mixed with equal volume of adjuvant. Two males and four females were controls and received a phosphate buffer mixed with equal volume of adjuvant. The mixtures were administered intradermally and subcutaneously at weekly intervals for 6 consecutive wk and blood samples collected weekly. The enzyme was antigenic by the coated tanned red blood cell method. After the third weekly immunization, precipitating antibodies were in the sera of animals that received the active enzyme. Hemagglutination titers increased during subsequent weeks and reached a maximum after the sixth weekly immunization. Antisera from animals immunized with heat-inactivated xanthine oxidase gave a positive response similar to that with animals immunized with the active enzyme. However, when the same antisera were tested with sheep red blood cells coated with heat-inactivated enzyme, no hemagglutination was observed. Ouchterlony double gel-diffusion tests showed that it may be possible to differentiate between antibodies elicited to active and heat-inactivated xanthine oxidase.
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PMID:Antigenicity of bovine milk xanthine oxidase in guinea pigs. 81 73

The effects of prolonged intravenous administration of bovine milk xanthine oxidase (EC 1.2.3.2.) on blood lipids and arterial integrity were measured to determine if the administration of this enzyme produces metabolic changes conducive to plaque formation. New Zealand White rabbits were injected intravenously with bovine milk xanthine oxidase at 4-day intervals during a 13-week test period. At the end of the test period, the rabbits were killed and blood, heart, aorta, liver, and kidneys were collected and evaluated. Rabbits injected with phosphate buffer or acid-denatured xanthine oxidase for the same length of time served as negative controls. Additional rabbits fed a diet containing 3% added cholesterol for the same time period served as positive controls. The administration of xanthine oxidase in large amounts over a prolonged period did not alter serum cholesterol or triglyceride levels and did not reduce plasmalogen levels in the aorta or heart. Xanthine oxidase administration did not induce arterial plaque formation. Cholesterol feeding over the same time period increased serum cholesterol levels, reduced liver xanthine oxidase activity levels and resulted in a marked development of arterial plaques. Althouth xanthine oxidase activity was found in liver from all rabbits, enzyme activity was not detectable in aorta, heart or kidneys from any rabbit. Free or complexed bovine milk xanthine oxidase could not be demonstrated in heart, aorta, liver or kidneys from any of the rabbits with immunodiffusion or with immunofluorescent techniques. The study showed that when large intravenous doses of bovine milk xanthine oxidase were given to rabbits, the enzyme was not deposited in heart, aorta, liver or kidneys. The study also showed that large intravenous doses of xanthine oxidase over prolonged periods did not deplete arterial or coronary tissue plasmalogens, and did not induce arterial plaque formation.
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PMID:Bovine milk xanthine oxidase, blood lipids and coronary plaques in rabbits. 87 Jun 48

Sprague-Dawley rats were vibrated for 4 min in one of 12 combinations of G levels (+/-2, +/-4, or +/-8 GX) and frequency ranges (12-61, 62-111, 112-161, or 162-211 HZ). The animals were restrained and conscious during vibration. Plasma calcium, magnesium and inorganic phosphate concentrations as well as xanthine oxidase activities were determined for each animal at various times before and after vibration. Vibration at specific G levels induced physiological changes in plasma calcium, magnesium, and xanthine oxidase levels. Plasma inorganic phosphate concentrations appeared to increase with an increase in the displacement of vibration. All of the effects observed occurred within 24 h of vibration treatment. An effect of the frequency of vibration was not observed with any of the parameters examined. Factors involved in performing the experiments also were able to induce certain physiological changes, viz., the level of plasma calcium and xanthine oxidase activity.
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PMID:Effects of mechanical vibration on rat plasma calcium, magnesium, phosphate, and xanthine oxidase. 121 41

Kinetic characteristics for reactivity of SH-groups of milk xanthine oxidase were obtained under different conditions. Two types of SH-groups with rate constant values, differing by a factor of about 50, were found in a phosphate buffer at pH 7.0. The slow stage of reaction is followed by protein precipitation. The number of fast- (12) and slowly-reacting (60) groups were calculated from the kinetic data. The blocking of the fast-reacting groups occurs without loss of the enzyme activity. The values of activation energy for the fast- and slowly-reacting groups are 15 and 48 kcal/mol respectively. The formation of the enzyme-substrate complex stabilizes the enzyme molecule; the number of fast-reacting SH-groups and the rate constant values for both types of groups remain unchanged, whereas the number of slowly-reacting SH-groups markedly decreases (37). The values of activation energy for both types of SH-groups show no changes in the presence of substrate. Conformations of the enzyme in different denaturating solvents were characterized by a number of SH-groups, reacting with p-chloromercurybenzoate. 54 groups are exposed in solutions of groups exposed in 7.0-8.5 M urea solutions is 35-38. In all solvents studied the protein molecule is probably not completely unfolded, since the number of exposed SH-groups is less than the full number of SH-groups determined by the amino acid analysis. Only 42 SH-groups reacted with 5,5'-dithiobis-(2-nitrobenzoic acid) under the same conditions.
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PMID:[A kinetic study of the reactive capabilities of xanthine oxidase sulfhydryl groups with regard to n-chlormercuribenzoate]. 127 74


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