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)

Foals with combined immunodeficiency had normal levels of purine salvage pathway enzymes, including adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase.
 ...
PMID:Evaluation of adenosine deaminase and other purine salvage pathway enzymes in horses with combined immunodeficiency. 81 21

1. 2',3'-Dideoxyinosine (ddI) has potent activity against human immunodeficiency virus (HIV). It is converted within target cells to its active form dideoxyadenosine triphosphate(ddA-TP). 2. In addition to the intracellular formation of ddA-TP, ddI can be broken down to hypoxanthine, by purine nucleoside phosphorylase (PNP) and to uric acid, by xanthine oxidase. Since PNP is present in red blood cells we have examined the metabolism of [14C]-ddI by human blood. 3. When incubated with whole blood at 37 degrees C, ddI was extensively metabolised, principally to hypoxanthine (50.4 +/- 12.5% formed at 6 h; mean +/- s.d.; n = 16). Small amounts of uric acid were formed (3.8 +/- 2.4%). 4. ddI breakdown was temperature dependent, being virtually negligible at 4 degrees C. Metabolism to hypoxanthine occurred within red blood cells. 5. The short half-life of ddI in patients is probably the result of both hepatic and erythrocytic metabolism.
 ...
PMID:Metabolism of 2',3'-dideoxyinosine (ddI) in human blood. 157 55

An anti-HIV (human immunodeficiency virus) phenolic constituent, licopyranocoumarin (4), and two other new phenolics named licoarylcoumarin (5) and glisoflavone (6) were isolated from Si-pei licorice (a commercial licorice; root and stolon of Glycyrrhiza sp. from the north-western region of China) using droplet countercurrent chromatography and centrifugal partition chromatography, and their structures were assigned based on chemical and spectroscopic data. Kaempferol 3-O-methyl ether (7) and licocoumarone (8) were also isolated from the licorice. The inhibitory effects of ten licorice phenolics on xanthine oxidase were examined. Licochalcone B (1), glycyrrhisoflavone (2), 8 and licochalcone A (19) showed 50% inhibition at the concentration of 1.3-5.6 x 10(-5) M.
 ...
PMID:Phenolic constituents of licorice. II. Structures of licopyranocoumarin, licoarylcoumarin and glisoflavone, and inhibitory effects of licorice phenolics on xanthine oxidase. 263 45

The importance of intact adenosine deaminase (ADA) activity in the generation of superoxide anion by xanthine oxidase has been disputed in studies using human neutrophils or mouse macrophages. The latter demonstrated a positive correlation between ADA activity and superoxide production during phagocytosis. The immunodeficiency in inherited ADA deficiency was related to a defect in this process. Since there is considerable interspecies variation in the tissue distribution of xanthine oxidase, the metabolism of [8-14C]deoxyadenosine (dAR), the toxic metabolite which accumulates in inherited ADA deficiency, was investigated in human peritoneal macrophages. Evaluation of the distribution of radiolabel in both cell and medium demonstrated that human macrophages with intact ADA metabolize dAR under physiological conditions to deoxyinosine and hypoxanthine exclusively. The hypoxanthine is further metabolized within the cell to ATP and GTP, via IMP. No xanthine or uric acid could be detected, confirming that in human macrophages xanthine oxidase activity is insignificant, as it is in most other human cells and tissues, except liver and intestinal mucosa. Thus production of superoxide radicals in such cells via this route would be impossible, and consequently unaffected either by ADA deficiency or the xanthine oxidase inhibitor allopurinol.
 ...
PMID:Superoxide radicals, immunodeficiency and xanthine oxidase activity: man is not a mouse! 298 25

The metabolic causes for immune impairment in patients with severe chronic inflammatory diseases have not been clearly defined. Recently, the overproduction of poly(ADP-ribose) in resting lymphocytes with unrepaired DNA strand breaks has been suggested to contribute to immune dysfunction in adenosine deaminase-deficient patients. Our experiments have determined to what extent DNA damage and poly(ADP-ribose) synthesis might also explain the impaired mitogen responsiveness of PBL exposed to toxic oxygen species. Treatment of normal resting human lymphocytes with xanthine oxidase and hypoxanthine dose-dependently induced DNA strand breaks and triggered the rapid synthesis of poly(ADP-ribose). Subsequently, NAD+ and ATP pools decreased precipitously. Lymphocytes exposed previously to the enzymatic oxidizing system did not synthesize DNA after stimulation with PHA. However, if the medium was supplemented with 3-aminobenzamide or nicotinamide, two compounds that inhibit poly(ADP-ribose) formation, cellular NAD+ and ATP pools were preserved, and the lymphocytes responded vigorously to a mitogenic challenge. Excessive poly(ADP-ribose) synthesis, provoked by DNA strand breakage, may represent a common pathway that connects the immunodeficiency syndromes associated with (a) exposure of lymphocytes to toxic oxygen species during chronic inflammatory states, (b) adenosine deaminase deficiency, and (c) certain DNA repair disorders.
 ...
PMID:Lymphocyte dysfunction after DNA damage by toxic oxygen species. A model of immunodeficiency. 395 May 45

During phagocytosis and membrane perturbation, mouse macrophages generate superoxide in direct proportion to their intracellular adenosine deaminase activity. It is proposed that since adenosine deaminase controls the amount of substrate available to xanthine oxidase, and the latter produces superoxide during turnover of its substrates, the purine salvage pathway is an important contributor to the superoxide requirement of macrophages. It is further proposed that this may be the basis for the mechanism of the association of adenosine deaminase deficiency with immunodeficiency.
 ...
PMID:Adenosine deaminase activity and superoxide formation during phagocytosis and membrane perturbation of macrophages. 626 29

Phagocytosis and membrane perturbation in mouse macrophages results in an increased superoxide ion production which is in direct proportion to the concomitant increase in adenosine deaminase activity. Since adenosine deaminase activity controls the amount of substrate available to xanthine oxidase, and the latter produces superoxide during turnover of its substrates, it is proposed that the purine salvage pathway is an important source of the superoxide requirement of macrophages. It is further proposed that this may be the basis, at least in part, for the mechanism of the association of immunodeficiency with adenosine deaminase deficiency.
 ...
PMID:Positive correlation between adenosine deaminase activity and superoxide formation during phagocytosis. 630 Feb 72

Neutrophils and macrophages generate superoxide anion during the respiratory burst in response to various stimuli, including microorganisms. It has recently been proposed that an important source of superoxide anion during the respiratory burst that stimulates murine macrophages is the sequential metabolism of adenosine via adenosine deaminase and xanthine oxidase to uric acid. Thus, the immunodeficiency state associated with adenosine deaminase deficiency may be caused at least in part by a defect in superoxide anion generation. The ability to generate superoxide anion of stimulated neutrophils isolated from three children with adenosine deaminase deficiency and associated severe combined immunodeficiency was tested. Neutrophils from all three patients were able to generate superoxide anion. One of these generated 19.1 nmol cytochrome c reduced/10(6) cells (normals = 5.3-33.0, mean 18.4 +/- 7.1) while the other two generated low normal levels. Neutrophils from all three children also generated more superoxide anion after addition of exogenous adenosine deaminase. Thus, no evidence to support a role for cellular adenosine deaminase in the release of superoxide anion by stimulated neutrophils was found. Although neutrophils from patients deficient in adenosine deaminase appear to have no inherent defect in the generation of superoxide anion, the abnormally high concentrations of adenosine found in the plasma of these patients could, in vivo, secondarily, inhibit superoxide anion release.
 ...
PMID:Adenosine deaminase is not required for the generation of superoxide anion. 632 Oct 74

Bio-normalizer, a natural Japanese health food prepared by the fermentation of Carica papaya, exhibits therapeutic properties against various pathologies including tumors and immunodeficiency. To understand the mechanism of bio-normalizer's therapeutic effects, we studied its action on the production of active oxygen species in cell-free systems (the Fenton reaction, the xanthine-xanthine oxidase system, and the hydrogen peroxide-hypochloride or hydrogen peroxide-horseradish peroxidase systems) and by human blood neutrophils and erythrocytes and rat peritoneal macrophages. Bio-normalizer efficiently inhibited the formation of oxygen radicals in cell-free systems and partly decreased spontaneous and menadione-stimulated superoxide production by erythrocytes, but manifested both stimulatory and inhibitory effects on oxygen radical release by dormant and activated phagocytes (neutrophils and macrophages). We suggest that bio-normalizer is able to enhance the intracellular production of innocuous superoxide ion and, at the same time, to diminish the formation of reactive hydroxyl radicals, perhaps by the inactivation of ferrous ions, the catalysts of the superoxide-driven Fenton reaction. We also propose that the normalization of an organism's superoxide level is one of the molecular mechanisms of bio-normalizer activity.
 ...
PMID:Effects of bio-normalizer (a food supplementation) on free radical production by human blood neutrophils, erythrocytes, and rat peritoneal macrophages. 874 24

(-)-beta-D-2-Aminopurine dioxolane (APD) and (-)-beta-D-2-amino-6-chloropurine dioxolane (ACPD) are recently synthesized dioxolanylpurine nucleoside derivatives being developed as potential prodrugs for the antiviral nucleoside analog (-)-beta-D-dioxolane guanine (DXG). In vitro, APD and ACPD are converted to DXG by xanthine oxidase and adenosine deaminase, respectively. The purpose of this study was to evaluate the preclinical pharmacokinetics of APD and ACPD and their potential for generating sustained levels of the parent nucleoside, DXG, in rhesus monkeys following oral administration. Both nucleoside derivatives were rapidly absorbed, with similar peak concentrations achieved within 1 h after administration. However, concentrations of APD were more markedly sustained than those of ACPD. Both prodrugs yielded DXG, but significantly higher serum concentrations of DXG and area under the concentration-time curve values were observed following administration of APD. In addition, APD produced higher concentrations of prodrug and DXG in cerebrospinal fluid than did ACPD. Thus, the results of this pharmacokinetic study suggest that APD is likely to serve as a better prodrug of DXG and should be considered for clinical trials for antiviral therapy against human immunodeficiency virus and hepatitis B virus.
 ...
PMID:Pharmacokinetics of (-)-beta-D-2-aminopurine dioxolane and (-)-beta-D-2-amino-6-chloropurine dioxolane and their antiviral metabolite (-)-beta-D-dioxolane guanine in rhesus monkeys. 889 Nov 40


1 2 3 Next >>