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)

We investigated the influence of CIM and HIS on the SUP and CH in the SUP generating cell-free xanthine oxidase system and in human neutrophils. As measured by CCR or CH, we found that HIS inhibited SUP output in both systems. The HIS concentration required for a measurable inhibition was somewhat higher in the xanthine oxidase system than in neutrophils. CIM increased CH in neutrophils significantly. A similar effect of CIM was not observed in the xanthine oxidase system. CIM antagonized in neutrophils the effect of HIS. However, a five or ten times higher molar concentration of CIM than of HIS was necessary to produce this effect. The antagonistic effect of CIM was not found in the xanthine oxidase system within the concentrations applied. In addition to an interaction of HIS with neutrophils on the cellular level, we suggest a superoxidase scavenging effect caused by HIS. At the present no suggestions can be made regarding the observed SUP output stimulating activity of CIM.
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PMID:Interaction of cimetidine and histamine with superoxide generated in a cell-free system and in neutrophils. 303 67

The sigmoidal time course of haemoglobin oxidation by nitrite, involving an initial slow reaction accompanied by a subsequent rapid reaction, was extensively explored. The initial slow reaction was much prolonged by the addition of superoxide dismutase to the reaction mixture. On the other hand, in the presence of superoxide anion generated by xanthine oxidase systems, the slow phase disappeared and the reaction changed to first-order kinetics. The oxidation of intermediate haemoglobins [defined as haemoglobin tetramer in which different chains (alpha- or beta-) are in the ferric state and in the ferrous state] such as (alpha 2+ beta 3+)2 and (alpha 3+ beta 2+)2 also proceeded in a sigmoidal manner. Similar effects of superoxide anion on these reactions were observed. Since the intermediate haemoglobins such as (alpha 2+ beta 3+)2 and (alpha 3+ beta 2+)2 were found to be produced by the oxidation of haemoglobin by nitrite, the changes in oxyhaemoglobin, intermediate haemoglobins and methaemoglobin during the reaction were followed by isoelectric-focusing electrophoresis. The amounts of (alpha 2+ beta 3+)2 were larger than those of (alpha 3+ beta 2+)2 at the initial stages of the reaction, suggesting that there is a functional difference between alpha- and beta-chains in the oxyhaemoglobin tetramer. On the basis of these results, a reaction model of the haemoglobin oxidation by nitrite was tentatively proposed. The changes in oxyhaemoglobin, intermediate haemoglobins and methaemoglobin were well fitted to the simulation curves generated from the reaction model. Details of the derivation of the equations used for kinetic analysis have been deposited as Supplement SUP 50112 (5 pages) with the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K. from whom copies may be obtained on the terms indicated in Biochem. J. (1978) 169, 5.
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PMID:Involvement of superoxide anion in the reaction mechanism of haemoglobin oxidation by nitrite. 627 3