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

1. Ethanol metabolism in slices or homogenates of transplantable hepatocellular carcinoma HC-252 (HC-252) was 50 to 60% of the rate found in host liver slices or homogenates when they were expressed per gram of tissue wet weight and 70 to 80% of the liver when the rates were expressed per milligram of tissue protein. At 10 mM ethanol, the activities of alcohol dehydrogenase in tumor and liver supernatants were comparable. 2. Tumor microsomes did not oxidize ethanol in the presence of a NADPH-generating system, indicating the absence of the microsomal ethanol-oxidizing system and catalase-mediated peroxidation of ethanol. The HC-252 microsomes were contaminated with catalase, and acetaldehyde production occurred in the presence of a H2O2-generating system (xanthine oxidase). The virtual absence of ethanol oxidation and drug metabolism (aminopyrine demethylase and aniline hydroxylase) in HC-252 microsomes may be due to the low activities of NADPH-cytochrome c reductase, NADPH oxidase, and NADPH-dependent oxygen uptake. 3. Microsomal oxidation of ethanol was present in Morris hepatoma 5123C, a well-differentiated tumor of intermediate growth rate, while activity was negligible in microsomes from Morris hepatoma 7288CTC, a less differentiated tumor. Microsomal NADPH oxidase was present in the well differentiated tumor 5123C but was lacking in the less differentiated tumor 7288CTC. Several microsomal, mitochondrial, and cytosolic properties of HC-252 are similar to those of Morris hepatoma 7288CTC but differ from those of the more differentiated 5123C tumor and normal liver. 4. The content of mitochondrial protein in HC-252 was only 25% that of liver, and oxygen consumption per gram of tumor was only 28% that of the liver. When corrected for the mitochondrial protein content, oxygen uptake in tumor HC-252 and liver homogenates was comparable. Isolated tumor and liver mitochondria displayed comparable State 4 and 3 rates of oxygen consumption with succinate and glutamate as substrates. The activities of the reconstituted malate-aspartate and alpha-glycerophosphate shuttles were only slightly lower in isolated HC-252 mitochondria compared to liver mitochondria, when shuttles were reconstituted with purified enzymes. 5. Antimycin inhibited alcohol metabolism,and pyruvate stimulated alcohol metabolism, much less in tumor slices than in liver slices, suggesting the presence of an augmented mitochondria-independent, cytosolic mechanism for oxidizing reducing equivalents in the tumor. These factors suggest that oxidation of NADH is the limiting factor in ethanol metabolism. Whereas, in the liver mitochondrial reoxidation is predominant, in HC-252, cytosolic reoxidation of NADH also plays a major role.
 ...
PMID:Ethanol metabolism by a transplantable hepatocellular carcinoma. Role of microsomes and mitochondria. 13 37

An efficient scavenger for radiolytically generated hydroxyl (OH) radicals, p-nitrosodimethylaniline, was used to try to substantiate the presence of this oxygen radical species in several biochemical systems. Most of these systems which were investigated had previously been assumed to generate OH radicals, e.g. the autoxidation of 6-hydroxydopamine, the hydroxylating system NADH/phenazine methosulfate, and the oxidation of xanthine or acetaldehyde by xanthine oxidase. We did not observe inhibition of the bleaching of p-nitrosodimethylaniline in oxygenated solutions by other scavengers of OH radicals nor, in the case of xanthine/xanthine oxidase, by catalase and superoxide dismutase. We therefore conclude that, under biochemical conditions as opposed to radiolysis or photolysis, no freely diffusable OH radicals are formed. Rather, a strongly oxidizing OH-analogous complex is considered to represent the p-nitrosodimethylaniline-detectable species formed under these conditions.
 ...
PMID:On the nature of biochemically generated hydroxyl radicals. Studies using the bleaching of p-nitrosodimethylaniline as a direct assay method. 22 Dec 20

A spectrophotometric method for the determination of three forms of xanthine oxidoreductase, namely dehydrogenase (D), dehydrogenase-oxidase (D/O) and oxidase (O), is described. Enzymic fractions obtained from rat liver were found to contain either all three forms, or (under special conditions of preparation) only two forms, D and D/O. The conversion of form D leads to form D/O leads to form O in the presence of Cu2+ ions was shown. Form D/O acted with NAD+ as well as with O2 as electron acceptors, it exhibited greater affinity to NAD+ than to O2, and NAD+ abolished the oxidase activity of this form. Moreover, oxidase activity of form D/O was inhibited by NADH. These facts indicate that NAD+ and O2 compete for the same active site on the enzyme molecule.
 ...
PMID:Intermediate dehydrogenase-oxidase form of xanthine oxidoreductase in rat liver. 22 81

Xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) supplemented with an electron donor could catalyze the cis-trans isomerization of 3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide, 3-(5-nitro-2-furyl)-2-phenylacrylamide and 3-(5-nitro-2-furyl)-2-(2-furyl)acrylonitrile. The direction of isomerization (cis leads to trans, cis in equilibrium trans or trans leads to cis) is dependent on the chemical structure of these nitrofuran derivatives. Lipoyl dehydrogenase (NADH:lipoamide oxidereductase, EC 1.6.4.3), DT-diaphorase (NAD(P)H:(quinone-acceptor) oxidoreductase, EC 1.6.99.2) and liver microsomes could also catalyze the conversion of cis-3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide to its trans isomer in the presence of an appropriate electron donor. Such isomerizing activity of these enzymes is much higher than their nitro-reducing activity. In addition, the cis-trans isomerization of some nitrofuran derivatives was demonstrated with the liver slices and the small intestines of rats. A new cis-trans isomerization mechanism which is based on transfer of a single electron by an enzyme system to a nitrofuran derivative to give the radical-anion was proposed. This postulated mechanism was supported by the preliminary experiments using pulse radiolysis technique.
 ...
PMID:Enzymic cis-trans isomerization of nitrofuran derivatives: isomerizing activity of xanthine oxidase, lipoyl dehydrogenase, DT-diaphorase and liver microsomes. 45 30

A new method for the determination of guanase is described. Xanthine, the product of the guanase reaction, is oxidized by xanthine oxidase, forming uric acid and hydrogen peroxide. Hydrogen peroxide is further reduced to water by catalase in the presence of ethanol. The acetaldehyde formed in this reaction step is dehydrogenated NAD or NADP dependent by aldehyde dehydrogenase. The NADH or NADPH production is measured and utilized for the calculation of the guanase activity. The sensitivity of the method can be doubled by the addition of uricase, which oxidizes uric acid to permit the formation of another mole of hydrogen peroxide.
 ...
PMID:A new spectrophotometric assay for enzymes of purine metabolism. II. Determination of guanase activity. 48 57

Milk fat globule membranes (MFGM) and rough endoplasmic reticulum (RER) membranes were isolated from milk and lactating mammary gland from the cow and were characterized by biochemical and electron microscope methods in terms of gross composition (proteins, phospholipids, neutral lipids, cholesterol, RNA, and DNA) and purity. Both fractions contained significant amounts of a b-type cytochrome with several properties similar to those of cytochrome b5 from liver, as well as a rotenone-insensitive NADH- and NADPH-cytochrome c reductase. The b-type cytochrome content in the apical plasma membrane-derived MFGM was of the same order of magnitude as it was in RER membranes. It was characterized by a high resistance to extraction by low- and high-salt concentrations and nonionic detergents. MFGM contained much more flavin and much higher activities of xanthine oxidase than the RER membranes. The same redox components were found in MFGM and mammary RER from women, rats, mice, and goats, but in absolute contents great differences between the species were noted. The cytochromes described here differed from liver cytochrome b5 in some spectral properties. The alpha-band of the reduced hepatic cytochrome b5 is asymmetric with a maximum at 555 nm that is split into two distinct peaks at low temperatures. The alpha-band of the b-type cytochromes from MFGM and mammary RER appears as one symmetrical peak at about 560 nm that is not split at low temperatures. When treated with cyanide, MFGM and mammary microsomes showed difference spectra of a reduced b-type cytochrome. Under the same conditions, liver microsomes gave a completely different spectrum. These findings demonstrate the presence of a b-type cytochrome and associated redox enzymes in MFGM, i.e., a derivative of the apical cell surface membrane that is regularly used for envelopment of the milk fat globule during secretion.
 ...
PMID:Redox constituents in milk fat globule membranes and rough endoplasmic reticulum from lactating mammary gland. 85 33

NADH-FMN oxidoreductase has been proposed as an enzyme involved in the release of iron from ferritin. The effects of riboflavin and/or iron deficiencies and of dietary allopurinol on the activities of this enzyme and on the iron contents of liver, kidney and duodenum were investigated. Allopurinol, a xanthine oxidase inhibitor, did not affect organ enzyme activities nor iron contents. Riboflavin-deficient rats and iron-deficient rats both had significantly lower organ enzyme activities and iron contrnts than controls. Organ enzyme activities and iron contents of rats fed a diet deficient in both iron and riboflavin were significantly lower than those of controls. After dietary iron and/or riboflavin repletion, organ enzyme activities and iron contents increased. Rats fed an irons-overload diet had enzyme activities similar to that of controls, but organ iron contents were significantly increased over those of controls. Effects of riboflavin and/or deficiencies in rats on NADH-FMN oxidoreductase activities and iron contents of liver, kidney and duodenum appeared to be reversible by riboflavin and/or iron supplementation. The data support the view that NADH-FMN oxidoreductase may be a controlling enxyme in iron release from ferritin.
 ...
PMID:NADH-FMN oxidoreductase activity and iron content of organs from riboflavin and iron-deficient rats. 85 41

Triamcinoline acetonide (10 mg per kg of body weight a day) was administered to rabbit fed on a laboratory chow diet. The content of flavins in liver but not in kidney, muscle and brain started to decrease 24 h after a single dose. The activities of enzymes in the liver were determined: the activities of pyruvate dehydrogenase complex, lipoamide dehydrogenase (NADH:lipoamide oxidoreductase EC 1.6.4.3), NADH dehydrogenase (NADH : (acceptor) oxidoreductase EC 1.6.99.3) and D-amino acid oxidase (D-amino acid: oxygen oxidoreductase (deaminating) EC 1.4.3.3) were decreased but those of succinate dehydrogenase (succinate : (acceptor) oxidoreductase EC 1.3.99.1) and xanthine oxidase (xanthine : oxygen oxidoreductase EC 1.2.3.2) remained unchanged. The activities of enzymes in the kidney, however, remained unchanged except the decrease in the activity of pyruvate dehydrogenase complex.
 ...
PMID:Effect of triamcinolone administration on content of flavins in rabbit liver. 127 76

Two free radical generating systems, xanthine oxidase/hypoxanthine or phenazine methosulfate/NADH, were exposed to air plus He, N2, or Ar at partial pressures ranging from 0.2 to 6.0 MPa, and the rates of production of superoxide, hydroxyl, singlet O2, and H2O2 were measured. All three inert gases acted similarly to enhance the production of superoxide radicals by facilitating interactions between iron and H2O2, or O2 and organic radicals. These reactions occurred at quite low gas partial pressures, only 0.28 MPa, and hydrostatic pressures of up to 6.0 MPa had no effect on radical reactions. Enhanced radical production may be the basis for the inhibition of cellular growth mediated by inert gases, and inert gas enhancement of O2 toxicity.
 ...
PMID:Inert gas enhancement of superoxide radical production. 131 38

Picroliv, the active principle of Picrorhiza kurrooa, and its main components which are a mixture of the iridoid glycosides, picroside-I and kutkoside, were studied in vitro as potential scavengers of oxygen free radicals. The superoxide (O2-) anions generated in a xanthine-xanthine oxidase system, as measured in terms of uric acid formed and the reduction of nitroblue tetrazolium were shown to be suppressed by picroliv, picroside-I and kutkoside. Picroliv as well as both glycosides inhibited the non-enzymic generation of O2- anions in a phenazine methosulphate NADH system. Malonaldehyde (MDA) generation in rat liver microsomes as stimulated by both the ascorbate-Fe2+ and NADPH-ADP-Fe2+ systems was shown to be inhibited by the Picroliv glycosides. Known antioxidants tocopherol (vitamin E) and butylated hydroxyanisole (BHA) were also compared with regard to their antioxidant actions in the above system. It was found that BHA afforded protection against ascorbate-Fe(2+)-induced MDA formation in microsomes but did not interfere with enzymic or non-enzymic O2- anion generation; and tocopherol inhibited lipid peroxidation in microsomes by both prooxidant systems and the generation of O2- anions in the non-enzymic system but did not interfere with xanthine oxidase activity. The present study shows that picroliv, picroside-I and kutkoside possess the properties of antioxidants which appear to be mediated through activity like that of superoxide dismutase, metal ion chelators and xanthine oxidase inhibitors.
 ...
PMID:Picroliv, picroside-I and kutkoside from Picrorhiza kurrooa are scavengers of superoxide anions. 132 26


1 2 3 4 5 6 7 8 9 10 Next >>