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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Different selected enzymes, glucose oxidase (GOx), catalase (Cat), glucose dehydrogenase (GDH), horseradish peroxidase (HRP), and formaldehyde dehydrogenase (FDH), are used alone or coupled to construct eight different logic gates. The added substrates for the respective enzymes, glucose and H(2)O(2), act as the gate inputs, while the biocatalytically generated gluconic acid or NADH are the output signals that follow the operation of the gates. Different enzyme-based gates are XOR, INHIBIT A, INHIBIT B, AND, OR, NOR, Identity and Inverter gates. By combining the AND and XOR or the XOR and INHIBIT A gates, the half-adder and half-subtractor are constructed, respectively, opening the way to elementary computing by the use of enzymes.
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PMID:Logic gates and elementary computing by enzymes. 1682 40

The assembly of three concatenated enzyme-based logic gates consisting of OR, AND, XOR is described. Four biocatalysts, acetylcholine esterase, choline oxidase, microperoxidase-11, and the NAD+-dependent glucose dehydrogenase, are used to assemble the gates. Four inputs that include acetylcholine, butyrylcholine, O2, and glucose are used to drive the concatenated-gates system. The cofactor NAD+, and its reduced 1,4-dihydro form, NADH, are used as a reporter couple, and these provide an optical output for the gates. The modulus of the absorbance changes of NADH is used as a readout signal.
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PMID:Concatenated logic gates using four coupled biocatalysts operating in series. 1708 33

Biochemical systems that demonstrate the Boolean logic operations AND, OR, XOR, and InhibA were developed by using soluble compounds, which represent the chemical "devices", and the enzymes glucose oxidase (GOx), glucose dehydrogenase (GDH), alcohol dehydrogenase (AlcDH), and microperoxidase-11 (MP-11), which operated as the input signals that activated the logic gates. The enzymes were used as soluble materials and as immobilized biocatalysts. The studied systems are proposed to be a step towards the construction of "smart" signal-responsive materials with built-in Boolean logic.
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PMID:Boolean logic gates that use enzymes as input signals. 1839 83

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