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)

IgG1 is cleaved in vitro by granulocyte elastase into Fc, Fab and Fabc fragments. The cleaved products have been isolated by a series of chromatographic procedures and characterized with regard to molecular mass and isoelectric point. The Fc fragment has been previously shown to express at its N-terminal site a neoantigen which is specific for elastase (Kolb, G., Eckle, I., Heidtmann, H.-H., Neurath, F. & Havemann, K. (1988) Scand. J. Rheumatol. S75, 179-189). The production of superoxide radical anions in prestimulated neutrophils is inhibited dose-dependently by the elastase-generated Fc and Fabc fragments. Native IgG1 and Fab fragments show no inhibitory effect, nor do papain-generated Fc fragments. The degree of inhibition depends on the stimulus applied: half-maximal inhibition is obtained by 6 microM Fc after stimulation with 4 beta-phorbol and 2.4 microM after stimulation with fMet-Leu-Phe; neutrophils stimulated with serum-activated zymosan are not inhibited by IgG fragments. The effect of Fc is purely cellular; no inhibition of O2 generation can be produced by applying Fc to the xanthine oxidase/xanthine system. The fragments have no effect on the activation or activity of crude NADPH oxidase, which is the O2-forming enzyme system of neutrophils. Possible mechanisms are discussed by which Fc acts on stimulated neutrophils.
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PMID:Inhibition of neutrophil oxidative burst by elastase-generated IgG fragments. 215 63

Xanthine oxidase (EC 1.2.3.2) was purified from fresh cows' milk by differential centrifugation and hydroxylapatite chromatography in the absence of reducing agents and proteases. The purified isolate possessed an absorbance at 280 nm:absorbance at 450 nm ratio of 4.84; an absorbance (1 cm at 280 nm 1%) of 11.9; an activity:absorbance at 450 nm of 141, a specific activity of 3.59 units/mg; and detectable dehydrogenase activity. The enzyme preparation was obtained in a reversible oxidase form that could be partially converted to xanthine dehydrogenase in the presence of 10mM dithiothreitol or 1% mercaptoethanol. Amino acid analyses revealed that the enzyme was hydrophobic in nature and that lysine constituted its N-terminal residue. The protein contained 22 disulfide and 38 sulfhydryl groups, four of which were detectable in the undenatured protein complex. Discontinuous PAGE in the presence of selected dissociation agents did not result in further resolution. Sodium dodecyl sulfate-PAGE of the purified enzyme revealed a sharp zone with a molecular weight of 151,000 +/- 4000 (i.e., monomer). The purified enzyme exhibited oxidase activity in the presence of 6 M urea and following limited proteolysis by trypsin, chymotrypsin, plasmin, pancreatin, pepsin, and papain. Proteolyzed xanthine oxidase migrated as a single zone in polyacrylamide gels in the presence and absence of dissociating agents such as 1% mercaptoethanol and 6 M urea. Restricted digestion of xanthine oxidase by proteases was indicated by the presence of three major zones with molecular weights ranging from 85,000 to 100,000, 30,000 to 35,000, and 18,000 to 20,000 commonly observed in SDS gels. Amino acid profiles of the principal peptidyl fragments of trypsin-cleaved xanthine oxidase indicated their hydrophobic nature and lysine as the N-terminal residue for all fragments.
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PMID:Characteristics of purified cows' milk xanthine oxidase and its submolecular characteristics. 339 6

1. The xanthine oxidase of cow's milk, crude or purified, appears as an oxidase (type O), and can be converted almost completely into a NAD(+)-dependent dehydrogenase (type D) by treatment with dithioerythritol or dihydrolipoic acid, but only to a small extent by other thiols. 2. The D form of the enzyme is inhibited by NADH, which competes with NAD(+). 3. The kinetic constants of the two forms of the enzyme are similar to those of the corresponding forms of rat liver xanthine oxidase. 4. Milk xanthine oxidase is converted into an irreversible O form by pretreatment with chymotrypsin, papain or subtilisin, but only partially with trypsin. 5. The enzyme as purified shows a major faster band and a minor slower band on gel electrophoresis. The slower band is greatly reinforced after xanthine oxidase is converted into the irreversible O form by chymotrypsin.
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PMID:Milk xanthine oxidase type D (dehydrogenase) and type O (oxidase). Purification, interconversion and some properties. 435 4

The activities of superoxide dismutase (SOD) and several proteases were measured in kidney of mice treated with allopurinol in order to elucidate the mechanism of prophylactic action of allopurinol against chemotherapy-induced stomatitis. The following results were obtained. Following 3 day administration of allopurinol 20 mg/day per os (Group C), the concentrations of allopurinol and oxipurinol in the renal tissue were 203.9 +/- 52.1 and 1141.7 +/- 194.8 micrograms/g, respectively. The SOD activity was significantly lower in Group C than in the untreated control group (p < 0.01). The enzyme activities of papain and trypsin were suppressed in Group C. However, the other proteases tested were not affected by the administration of allopurinol, indicating only weak anti-protease action of allopurinol. These results suggest that allopurinol may be effective to prevent chemotherapy-associated stomatitis via both direct and indirect actions to oral mucosa, that include inhibitory actions on xanthine oxidase as well as protease.
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PMID:Prophylactic action of allopurinol against chemotherapy-induced stomatitis--inhibition of superoxide dismutase and proteases. 879 95