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Substrate (chemistry)

About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.


Papers
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Patent
Yasusi Niiyama1, Kenshi Sugahara1
25 Nov 1985
TL;DR: In this article, an electrochemical sensor is formed having a working electrode for detecting hydrogen peroxide surrounded by a cylinder portion, and with an enzymecontaining membrane at its tip.
Abstract: An electrochemical sensor is formed having a working electrode for detecting hydrogen peroxide surrounded by a cylinder portion, and with an enzymecontaining membrane at its tip. The membrane has a porous layer permeable to hydrogen peroxide between a layer containing an immobilized enzyme capable of decomposing hydrogen peroxide and a layer containing an immobilized enzyme capable of decomposing a substrate to form hydrogen peroxide. The cylinder portion is embedded in the layer containing the hydrogen peroxide decomposing enzyme and surrounds the working electrode such that the electrode is in contact with the porous layer but is not in contact with the layer containing the hydrogen peroxide decomposing enzyme. The layer containing the hydrogen peroxide forming enzyme is on a side of the porous layer opposite the electrode so as not to contact the electrode. Activity of the hydrogen peroxide decomposing enzyme is no more than one-fourth of the activity of the hydrogen peroxide forming enzyme. The electrochemical sensor reduces base line elevation after measurement action has been discontinued and measurement of a next sample is restarted.

117 citations

Journal ArticleDOI
TL;DR: Results, demonstrating the substrate preference for histamine and 1-methylhistamine, were unanticipated given the available literature and the availability of large quantities of highly purified enzyme.
Abstract: Human kidney diamine oxidase has been overexpressed as a secreted enzyme under the control of a metallothionein promoter in Drosophila S2 cell culture. This represents the first heterologous overexpression and purification of a catalytically active, recombinant mammalian copper-containing amine oxidase. A rapid and highly efficient purification protocol using chromatography on heparin affinity, hydroxyapatite, and gel filtration media allows for the recovery of large quantities of the recombinant enzyme, which is judged to be greater than 98% homogenous by SDS/PAGE. The availability of large quantities of highly purified enzyme makes it now possible to investigate the spectroscopic, mechanistic, functional, and structural properties of this human enzyme at the molecular level. Visible absorption, circular dichroism, electron paramagnetic resonance, and resonance Raman spectroscopic results are presented. The recombinant enzyme contains the cofactors 2,4,5-trihydroxyphenylalaninequinone and copper at stoichiometries of up to 1.1 and 1.5 mol per mol homodimer, respectively. In addition, tightly bound and stoichiometric calcium ions were identified and proposed to occupy a second metal-binding site. The apparent molecular weight of the recombinant protein, determined by analytical ultracentrifugation, suggests 20–26% glycosylation by weight. Detailed kinetic studies indicate the preferred substrates (k cat/K M) of human diamine oxidase are, in order, histamine, 1-methylhistamine, and putrescine, with K M values of 2.8, 3.4, and 20 µM, respectively. These results, demonstrating the substrate preference for histamine and 1-methylhistamine, were unanticipated given the available literature. The pH dependence of k cat for putrescine oxidation gives two apparent pK a values at 6.0 and 8.2. Tissue-specific expression of the human diamine oxidase gene was investigated using an mRNA array. The relevance of this work to earlier work and the suggested physiological roles of the human enzyme are discussed.

117 citations

Journal ArticleDOI
TL;DR: A kinetic model capable of describing species concentrations measured experimentally during the Fenton-mediated oxidation of p-hydroxybenzoic acid is presented and the role quinones play in the catalytic redox cycling of iron and the overall effect on the oxidative treatment performance of the system is highlighted.
Abstract: As Fenton (and Fenton-like) chemistry is increasingly implicated in a variety of areas and applications, an understanding of the mechanism and rates governing the system becomes relevant for a growing number of disciplines and purposes. In this work a kinetic model capable of describing species concentrations measured experimentally during the Fenton-mediated oxidation of p-hydroxybenzoic acid (pHBA) is presented and discussed. Experiments were conducted in the dark at low pH using reagent and substrate concentrations ranging from 100 μM to 2 mM. Analysis of the experimental and modeling results reveals that redox reactions between Fe and quinone or quinone-like compounds are essential for the model to qualitatively predict species concentration profiles observed in the laboratory. The quinone and quinone-like compounds generated as byproducts during the oxidation of pHBA act as reducing agents toward Fe(III), thereby assisting the redox cycling of Fe and increasing degradation of the target substrate. Th...

117 citations

Journal ArticleDOI
T. Engel1, Karl-Heinz Rieder1
TL;DR: In this article, the adsorption of H2 on Ni(110) has been studied using He and H2 diffraction and four homogeneous ordered phases as the coverage is increased between 0.7 and 1.6 at a substrate temperature of 100 K were observed.

117 citations

Journal ArticleDOI
TL;DR: An overview of the various aspects of enzymology, enzyme catalysis, enzyme immobilization and modulation of enzyme activity with special emphasis on modulation through different types of nanoparticles including their synthesis, characterization and applications is given.

116 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202214
2021807
20201,053
20191,064
20181,112
20171,024