Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The detailed procedure for a new fluorometric assay for total diamines in human urine is described. The diamines were purified from the urine by cation-exchange chromatography and incubated with human placental diamine oxidase. Hydrogen peroxide formed in the diamine oxidase reaction was measured fluorometrically by converting homovanillic acid to a highly fluorescent compound in the presence of peroxidase. Because of its simplicity and high sensitivity, our present method seems useful for routine clinical investigation. The data obtained from normal subjects and patients suffering from various forms of cancer are also presented.
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PMID:A fluorometric assay for total diamines in human urine using human placental diamine oxidase. 678 7

The advantages and disadvantages of previous methods for the routine estimations of serum mono and diamine oxidase are reviewed. 4-hydroxy-3-methoxy phenyl acetic acid reacts wtih hydrogen peroxide and peroxidase to form an intensely fluorescent substance, and a simple method using this reaction as a basis for the estimation is described. The results are tabulated and discussed.
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PMID:A simple routine method for mono and diamine oxidase estimation in human serum. 678 89

A simple and sensitive colorimetric assay for serum diamine oxidase (DAO) activity was based on a coupled reaction with peroxidase and a new chromogen, 10-(carboxymethyl-aminocarbonyl)-3,7-bis(dimethylamino) phenothiazine sodium salt (DA-67). In the presence of peroxidase and DA-67, peroxidase catalyzes the formation of methylene blue having an absorption maximum at 668 nm. The proposed method eliminates the interferences occurring in serum with use of ascorbate oxidase and stops the reaction with sodium diethyldithiocarbamate, leaving the methylene blue in the reaction mixture stable for about 2 h. Low normal basal values of serum DAO can be determined in the range 2.8-9.0 units/l. Since all reagents are commercially available the method is suitable for the clinical laboratory.
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PMID:Sensitive colorimetric assay of serum diamine oxidase. 807 Jan 35

The present paper describes a quick and simple enzymic method for evaluating histamine content in fish. After preparing a perchloric acid extract, it was neutralized to pH 6.8 with KOH. The action of a diamine oxidase on the histamine caused the formation of hydrogen peroxide. The addition of a second enzyme, a peroxidase, in the presence of hydrogen peroxide and a chromogen (leuco crystal violet) in reduced form (colourless) facilitated its oxidation into crystal violet (coloured). Following a two-hour incubation period, absorbance was measured at 596 nm. The correlation between histamine level and absorbance was acceptable in the concentration range from 3 to 30 mg/kg of histamine (r = 0.9946; p < 0.001). The accuracy of the method, expressed by CV, varied between 2.6% and 4.9%, and the recovery between 95.7% and 100.1%, depending on the concentration of analyte in the sample. The diamine oxidase used was very selective in relation to the histamine. Only the presence of tyramine, when histamine concentration was low (< 10 mg/kg), tended to interfere to a slight degree in the technique. Using a regression analysis, no statistically significant differences were found between the results obtained from the analysis of 18 tuna fish samples by HPLC and the enzymic method (r = 0.9867; p < 0.001).
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PMID:Determination of histamine in fish using an enzymic method. 822 28

Clonidine-displacing substance, thought to be the endogenous ligand for imidazoline receptors, has been identified recently as agmatine (1-amino-4-guanidinobutane). The similarity of this compound's structure to that of the diamine oxidase (DAO) inhibitor, aminoguanidine, led us to investigate the possibility that agmatine might be a substrate for this enzyme. The metabolism of agmatine by purified porcine kidney DAO was measured by a peroxidase-linked colorimetric assay. Agmatine was a substrate for this enzyme and, under the experimental conditions used here, was metabolised at a rate of 0.8 mumol agmatine h-1 (unit DAO activity)-1. In contrast, agmatine was a substrate neither for rat brain monoamine oxidase (MAO) -A or -B, nor for rat brown adipose tissue semicarbazide-sensitive amine oxidase (SSAO). The metabolism of agmatine by DAO was inhibited by aminoguanidine (IC50 14.9 nM) and by the antidepressant, phenelzine (IC50 1.95 microM). These results suggest that administration of DAO inhibitors may increase endogenous agmatine levels and thus alter imidazoline receptor densities. A review of the literature documenting ligand affinities for idazoxan-preferring (I2) imidazoline binding site subtypes and drug affinities for DAO enzymes indicates that some of the I2 sites described elsewhere may correspond to DAO and not to an imidazoline receptor.
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PMID:Metabolism of agmatine (clonidine-displacing substance) by diamine oxidase and the possible implications for studies of imidazoline receptors. 858 54

In need of a simple and sensitive method for detection of diamine oxidase (EC 1.4.3.6) activity in connection with diamine oxidase purification from human placenta, we have developed an enhanced chemiluminescence method using putrescine as substrate and horseradish peroxidase and luminol for the detection of the H2O2 produced by diamine oxidase. The method allows direct detection of small amounts of diamine oxidase in serum samples after agarose gel electrophoresis and allows visualization of diamine oxidase activity in tissue sections. Employing this method we have detected diamine oxidase in sera from cow, horse, monkey, rabbit, and pregnant women. On tissue sections from term human placenta diamine oxidase activity was exclusively localized to the maternal side and was concentrated in vessels and fibrinoid areas.
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PMID:In situ detection of diamine oxidase activity using enhanced chemiluminescence. 878 57

A continuous, peroxidase-linked spectrophotometric assay is described which is suitable for measuring monoamine and diamine oxidase and semicarbazide-sensitive amine oxidase activities in tissue homogenates. In the assay, 4-aminoantipyrine is oxidized and then condenses with vanillic acid to give a red quinoneimine dye. The absorbance at 498 nm is proportional to the amount of hydrogen peroxide released in the amine oxidase reaction. The molar absorption coefficient of the dye at pH 7.6 was 4654 M-1 cm-1. The method is suitable for use with any amine oxidase substrate which has a higher oxidation-reduction potential than does 4-aminoantipyrine. Following preincubation of rat liver homogenates with selective monoamine oxidase (MAO)-A and -B inhibitors, kinetic constants were obtained for metabolism of the mixed substrate, p-tyramine. Inhibition of MAO in rat liver homogenates was also measured following administration of the antidepressant, phenelzine. This inexpensive assay which employs reagents with low toxicity can thus be used to determine the degree of inhibition of MAO elicited by potential antidepressant and anti-parkinsonian agents. Drugs, their metabolites, and environmental toxins can also be screened as possible amine oxidase substrates or inhibitors, and kinetic constants for turnover of novel substrates can be determined.
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PMID:A continuous spectrophotometric assay for monoamine oxidase and related enzymes in tissue homogenates. 902 56

p-Aminoclonidine (apraclonidine) is a selective alpha 2 adrenergic agonist used to reduce intraocular pressure in the treatment of glaucoma. Use of apraclonidine is frequently associated with severe local allergic effects which warrant discontinuation of the drug in affected patients. We have assessed the oxidative lability of apraclonidine relative to a panel of adrenergic agonists and/or known allergens; amodiaquine, epinephrine, clonidine, and brimonidine. These compounds were compared by their electrochemical potentials as well as their oxidative lability in the presence of several oxidative enzyme systems (i.e., horseradish peroxidase, lactoperoxidase, myeloperoxidase, and diamine oxidase). The half-lives for enzymatic oxidation of these compounds were found to parallel the electrochemical oxidation potentials in the order: amodiaquine approximately epinephrine < apraclonidine << clonidine approximately brimonidine. The production of a reactive electrophilic intermediate of apraclonidine was demonstrated through the formation of two glutathione apraclonidine adducts from the horseradish peroxidase/H2O2-mediated oxidation of apraclonidine in the presence of glutathione. A mechanism for apraclonidine allergenicity in vivo is proposed wherein apraclonidine is bioactivated through oxidation to the bis-iminoquinone followed by protein conjugation to form an apraclonidine-protein hapten that elicits the immune response.
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PMID:A proposed mechanism for p-aminoclonidine allergenicity based on its relative oxidative lability. 930 86

Rhizobium leguminosarum colonizes host cells and tissues through infection threads, which are tubular in-growths of the plant cell wall. Monoclonal antibody MAC265 recognizes a plant matrix glycoprotein (MGP) associated with the lumen of these infection threads. This glycoprotein is also released in soluble form from the root tips of pea seedlings. In the presence of hydrogen peroxide, release of glycoprotein from root tips was not observed. Extractability from root tips was therefore used as the basis for investigating the peroxide-driven insolubilization of MGP and the possible involvement of two extracellular enzymes, peroxidase (POD) and diamine oxidase (DAO), was investigated. Release of MGP from root tips was enhanced by application of POD and DAO inhibitors (salicylhydroxamic acid and o-phenanthroline, respectively). Furthermore, release of MGP was inhibited by pretreatment of roots with putrescine (the substrate of DAO) and also by application of a partially purified extract of DAO from pea shoots. Following inoculation of pea roots with R. leguminosarum, elevated levels of DAO transcript were observed by reverse transcriptase-polymerase chain reaction (RT-PCR), but these then dropped to a low level from 4 to 10 days post inoculation, rising again in more mature nodules. In situ hybridization studies indicated that the bulk of the transcription was associated with the infected tissue in the center of the nodule. On the basis of these observations, we postulate that DAO may be involved in the peroxide-driven hardening of MGP in the lumen of infection threads and in the intercellular matrix.
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PMID:Involvement of diamine oxidase and peroxidase in insolubilization of the extracellular matrix: implications for pea nodule initiation by Rhizobium leguminosarum. 1075 4

Hydrogenperoxide (H(2)O(2)) is an end product of diamine and polyamine oxidation by their respective oxidase enzymes. A new sensitive assay method is based on a H(2)O(2)-titanium (Ti) complex formation as an indicator of H(2)O(2) production due to polyamine oxidation. The orange-yellow coloured H(2)O(2)-Ti complex was measured at 410 nm in a Shimadzu spectrophotometer. The assay conditions for maximum diamine oxidase (DAO) and polyamine oxidase (PAO) as standardized here using the hypocotyl tissues of Vigna catjang Endl. cv Pusa Barsati consisted of pH 7.4 (40 mM potassium phosphate buffer), 3 mM substrate (putrescine or spermine), 37 degrees C incubation temperature and 30 min incubation time in the presence of catechol (10(-2) M) used as an inhibitor of both peroxidase and catalase activity. The method described here was significantly more sensitive than the starch-iodide method [T.A. Smith, Biochem. Biophys. Res. Commun. 41 (1970) 1452-1456], which could be improved further if measured under the same assay conditions as described for the H(2)O(2)-Ti method. Sensitivity of the present method was tested by assaying DAO/PAO activity in auxin treated hypocotyls of Vigna and comparing it with the starch-iodide method in two other plant samples.
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PMID:A rapid and sensitive assay method for measuring amine oxidase based on hydrogen peroxide-titanium complex formation. 1096 Jul 28


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