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)

A sensitive electrochemical measurement system for hydroxyl radical (OH) was developed using enzyme-catalyzed signal amplification. In the presence of 2,6-xylenol as a trapping agent, glucose as a substrate, and pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) as a catalyst, the amperometric signal of the trapping adduct 2,6-dimethylhydroquinone (DMHQ) produced by the hydroxylation of 2,6-xylenol was able to be amplified and detected sensitively. The limit of detection (signal/noise [S/N]=3) for DMHQ was 1 nM. There was no significant interference from urate and other oxidizable compounds in the reaction mixture at the applied potential of 0V versus Ag/AgCl. This method was employed to observe the OH generation induced by the xanthine-xanthine oxidase (XO) system. The reaction rates of the DMHQ production induced from the xanthine-XO system in the presence and absence of various Fe(III) complexes and proteins were compared. Those with a free coordination site on the Fe atom effectively enhanced the OH generation.
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PMID:Sensitive electrochemical measurement of hydroxyl radical generation induced by the xanthine-xanthine oxidase system. 2518 Sep 84

Superoxide (O2.- ) generation in biological systems is achieved through some of the most complex enzymatic systems. Of these, only xanthine/xanthine oxidase has been used for in vitro biochemical studies. However, it suffers from limitations such as a lack of suitable heterologous expression system for xanthine oxidase and the irreversible consumption and low solubility of xanthine under physiological conditions. Herein, we report a redox-based, enzyme-catalyzed system, in which autoxidation of hydroquinone to quinone via semiquinone results in superoxide generation. Quinone is reduced back to hydroquinone by using the NfsB (oxygen-insensitive nitroreductase) enzyme of Escherichia coli strain K-12 and nicotinamide adenine dinucleotide phosphate hydride (NADPH; which is regenerated by using the glucose/glucose dehydrogenase system). This new system relies on quinones that can be recycled and have superior water solubility, as well as enzymes that are heterologously expressed. By using a variety of quinones and reaction conditions, along with a comparison of real-time fluorescence, menadione has been identified as the optimal substrate for superoxide generation. The new redox-based system presents a viable alternative for studying the biochemistry of superoxide under different physiological and pathological conditions.
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PMID:A Redox-Based Superoxide Generation System Using Quinone/Quinone Reductase. 2979 Jun 50