Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Indoleamine 2,3-dioxygenase was purified from rabbit small intestine to apparent homogeneity as judged by polyacrylamide gel electrophoresis and analytical ultracentrifugation. The native enzyme was a monomeric protein of a molecular weight of 41,000 +/- 1,000 with an s020,w value of 3.45 S. It had a relative abundance of hydrophobic amino acids such as valine, leucine, and isoleucine, and contained approximately 5% carbohydrate by weight. The estimated content of sugar residues per mol of enzyme was: galactose, 1.2; mannose, 2.6; N-acetylglucosamine, 5.2; and sialic acid, 0.8. One mole of enzyme had 0.8 mol of protoheme IX as a prosthetic group. However, copper was not detected in a significant amount and the ratio of copper to heme was less than 0.03. EPR spectra of the nitric oxide complex of the ferrous enzyme indicated that a nitrogen atom, possibly in an imidazole group, might be coordinated as the fifth ligand of the heme coenzyme. The anisotropic g values were gx = 2.08, gy = 1.98, and gz = 2.01. A single enzyme protein catalyzed the oxygenative ring cleavage of D- and L-tryptophan, D- and L-5-hydroxytryptophan, tryptamine, and serotonin. In addition, the purified enzyme had a peroxidase activity with guaiacol and potassium iodide as hydrogen donors, but not a catalase activity.
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PMID:Indoleamine 2,3-dioxygenase. Purification and some properties. 2 87

Thermostability of horseradish peroxidase modified by acetic, propionic, butyric, valeric and succinic anhydrides and trinitrobenzolsulfonic acid (TNBS) is studied within the temperature range of 56-80 degrees C. Acylation of 4 amino groups and arylation of 3 amino groups with TNBS are found to stabilize the enzyme, while modification of 6 groups decreases the enzyme stability. Chemical modification of peroxidase does not change its pH-dependence with respect to enzyme thermostability. Thermodynamic activation parameters of irreversible thermoinactivation are determined for native and modified peroxidase. Native peroxidase has deltaH not equal to = 30+/-1 kcal/mole and deltaS not equal to = 14 e. e.; modified by acid anhydrides peroxidase has deltaH not equal to within 64-87 kcal/mole and deltaS not equal to within 110-178 e. e. depending on the nature of a modifying agent. The effect of the structure of a radical introduced into the enzyme molecule, and of a number of modified epsilon-amino groups on thermoinactivation deltaH not equal to and deltaS not equal to values is discussed.
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PMID:[Chemical modification of lysine epsilon-NH2-groups in horseradish peroxidase. Its effect on enzyme stability. Temperature dependence of thermo-inactivation constants for native and modified peroxidase]. 3 26

The mechanism of antimicrobial activity of the peroxidase-hydrogen peroxide (H(2)O(2))-iodide (I(-)) system was investigated. Inhibition of respiration and loss of viability of Escherichia coli were used as measures of antimicrobial activity. Because the bacteria destroyed H(2)O(2), peroxidase antimicrobial action depended on the competition for H(2)O(2) between the bacteria and the peroxidase. Utilization of H(2)O(2) by the peroxidase was favored by (i) increasing either the peroxidase or the I(-) concentration, so as to increase the rate of oxidation of I(-), (ii) lowering the temperature to lower the rate of destruction of H(2)O(2) by the bacteria, and (iii) adding H(2)O(2) in small increments so as to avoid a large excess of H(2)O(2) relative to I(-). When utilization of H(2)O(2) by the peroxidase system was favored, the peroxidase system and iodine (I(2)) were equivalent. That is, antimicrobial action per mole of H(2)O(2) equaled that per mole of I(2). Also, identical antimicrobial action was obtained either by incubating the bacteria directly with the peroxidase system or by preincubating the peroxidase system so as to form I(2) and then adding the bacteria. On the other hand, peroxidase antimicrobial action could be obtained at low I(-) concentrations. These I(-) concentrations were lower than the concentration of I(2) that was required for antimicrobial action. It is proposed that peroxidase-catalyzed oxidation of I(-) yields I(2), which reacts with bacterial components to yield the oxidized components and I(-). The I(-) that is released can be reoxidized and participate again in the oxidation of bacterial components. In this way, I(-) acts as a cofactor in the peroxidase-catalyzed oxidation of bacterial components.
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PMID:Cofactor role of iodide in peroxidase antimicrobial action against Escherichia coli. 35 14

The chemical modification of bacterial components was studied following incubation of Escherichia coli with the peroxidase-hydrogen peroxide (H(2)O(2))-iodide (I(-)) antimicrobial system or with iodine (I(2)). The oxidation of cell sulfhydryls and the iodination of cell components were measured. Both the peroxidase system and I(2) oxidized sulfhydryls. When the I(-) concentration in the peroxidase system was greater than 100 muM, the peroxidase system and I(2) were equivalent. That is, sulfhydryl oxidation or killing per mole of H(2)O(2) equaled that per mole of I(2). These results were consistent with peroxidase-catalyzed oxidation of I(-) to yield 1 mol of I(2) per mol of H(2)O(2). Sulfhydryls were oxidized to yield sulfenic acids and free I(-). With I(-) concentrations in the range of 10 to 100 muM, the amount of sulfhydryls oxidized by the peroxidase system could exceed the amount of I(-). Because the oxidation of sulfhydryls to sulfenic acids did not consume I(-), one I(-) ion could participate in the oxidation of many sulfhydryls. With I(-) concentrations lower than 10 muM, complete oxidation of sulfhydryls was not obtained. Incorporation of I(-) into iodinated derivatives of bacterial components partly depleted the system of I(-) and limited the formation of I(2). These results indicated that antimicrobial activity was due to peroxidase-catalyzed oxidation of I(-) to I(2), followed by I(2) oxidation of cell components. There was a direct relationship between sulfhydryl oxidation and antimicrobial action. Although iodination of bacterial components accompanied sulfhydryl oxidation, the amount of I(-) incorporation was not directly related to antimicrobial action. Also, incorporation of I(-) interfered with antimicrobial action at low I(-) concentrations.
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PMID:Oxidation of Escherichia coli sulfhydryl components by the peroxidase-hydrogen peroxide-iodide antimicrobial system. 35 15

The interaction between immobilized antibodies against human immunoglobulin G (IgG) and the immunoenzyme complex IgG-peroxidase (IgG-P) was studied. The complex was obtained by covalent binding of IgG to peroxidase modified by sodium periodate. Study of the IgG-P binding kinetics and dissociation of the antibody-(IgG-P) complex showed that the antibodies immobilized on Sepharose reversibly interacted with IgG-P, similar to the antigen-antibody reaction in solution. The efficient values of the binding constants for the antibodies binding to Sepharose covalently and through the antigen-antibody bond are (2,2+/-0,5) 10(8) M-1 and (4,2+/-0,2) 10(8) M-1, respectively. The nature of a carrier and the immobilization method used do not significantly affect the rate of the complex binding to the antibodies. The activation energy of the reaction of IgG-P binding to the antibodies immobilized on Sepharose covalently and through the antigen-antibody bond is 7,3 and 4,1 kcal/mole, respectively. A procedure of titration of immobilized antibodies active sites with the antigen-enzyme complex is discussed.
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PMID:[Interaction between immobilized antibodies and the antigen-enzyme complex]. 43 70

Acetaminophen, p-aminophenol, and oxyphenbutazone interfere with the glucose oxidase/peroxidase method for glucose. Structurally related compounds that lack a free phenolic hydroxyl group (acetanilide, aniline, and phenylbutazone) do not interfere. During the analytical procedure acetaminophen is consumed. One mole of acetaminophen leads to an apparent loss of four moles of glucose. The hexokinase/glucose-6-phosphate dehydrogenase method (Boehringer Hexokinase method) is not affected by these substances.
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PMID:Interference by acetaminophen in the glucose oxidase-peroxidase method for blood glucose determination. 97 21

The kinetics of compound II formation, obtained upon mixing a highly purified horseradish peroxidase and hydrogen peroxide, was spectrophotometrically studied at three wavelengths in the absence of an added reducing agent. Our experiments confirm George's finding that more than one mole of compound II is formed per mole of hydrogen peroxide added. The new mechanism that we propose, contrary to the mechanism of George, is only valid when compound II is obtained in the absence of an added donor. Moreover, it is not inconsistent with the classical Chance mechanism of oxidation of an added donor by the system peroxidase -- hydrogen peroxide. According to this new mechanism, in the absence of an added donor, compound II formation involved two pathways. The first pathway is the monomolecular reduction of compound I by the endogenous donor, and the second pathway is the formation of two moles of compound II through the oxidoreduction reaction between one mole of peroxidase and one mole of compound I.
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PMID:Kinetic evidence of horseradish peroxidase oxidation by compound I. 114 26

Two patients (G2, G3) with iodine organification defect were studied. The first patient (G2), a 25-year-old women with no clinical hypothyroidism, had had her goiter for 10 years; 62% of the thyroidal iodine was released by perchlorate indicating iodine organification defect. The thyroid tissue obtained at thyroidectomy contained a normal concentration of thyroid peroxidase (I2 formation from I-) when tested after solubilization of the enzyme by trypsin and digitonin treatment of the particulate material. 1. The enzymatic activity (G2-TPO) behaved on DEAE cellulose chromatography very differently from those of hog (P-TPO) or another human goiter peroxidase (G1-TPO) (Pommier, et al., J Clin Endocrinol Metab 39: 69, 1974): the molarity of elution was 2M NaCl instead of 0.15 mM. 2. Both P-TPO and G2-TPO catalyzed iodide peroxidation (I- leads to I2) but the Km (iodide) value for G2-TPO was much lower (2.3 x 10(-2) M) when compared with that of P-TPO (3.7 x 10(-3) M) or G1-TPO (3.5 x 10(-3) M). In addition, the optimum pH for this reaction differed markedly (pH 6.1 instead of 7.9). 3. G2-TPO was poorly efficient in catalyzing the oxidation of gaiacol to tetragaiacol. 4. G2-TPO was unable to perform the iodination of non-iodinated goiter thyroglobulin whatever the pH and the iodide concentration. 5. Thyroglobulin from this goiter (G2) was almost not iodinated (0.0014%), i.e., 0.07 atoms iodine/mole thyroglobulin), and its total content in the gland was very low (0.3-4 g/1000 g wet tissue instead of 25 g). A clear discrepancy was thus shown between the euthyroid state of this patient and the total lack of iodinating activity of the isolated peroxidase. The second patient (G3), a 17-year-old man with clinical hypothyroidism, had had his goiter for 5 years. 100% of the thyroidal iodine was released by perchlorate indicating a complete iodine organification defect. The thyroid tissue obtained at thyroidectomy contained no peroxidase activity when tested before and after treatment of the particulate material by trypsin and digitonin and even in the presence of hematin. Thyroglobulin from this goiter, which was almost non-iodinated (0.0014%), was present in normal amounts in the gland (congruent to 25 g/1000 g).
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PMID:Thyroid iodine organification defects: a case with lack of thyroglobulin iodination and a case without any peroxidase activity. 126 32

2-Thiazoline-2-thiol is an antithyroid agent that strongly reduces thyroid hormone levels. Synthesis of these hormones is catalyzed in vivo by thyroid peroxidase. The interaction of this drug with molecular iodine and its effect on peroxidase activity were investigated. Iodine and 2-thiazoline-2-thiol form a complex of the charge transfer type of 1:1 stoichiometry characterized by a formation constant of 2,527 l.mole-1 at 20 degrees C. This drug was found to inhibit both horseradish peroxidase and lactoperoxidase (used as a model of thyroid peroxidase) in a competitive manner, giving inhibition constants of 5.7 mM and 0.13 mM, respectively. T3 and T4 levels were reduced significantly after a three-week administration of this drug to a group of 10 rats. Histological examination of the thyroid gland showed the presence of a cylindrical epithelium, which is indicative of hyperactivity of the gland. The results indicated that 2-thiazoline-2-thiol acts on both molecular iodine and thyroid peroxidase.
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PMID:Sites of action of 2-thiazoline-2-thiol on biogenesis of thyroid hormones. 138 Sep 99

We examined the influence of different staining techniques [(three-step immunoperoxidase technique (IP); alkaline phosphatase-anti-alkaline phosphatase technique (APAAP)] on the quantitative evaluation of Ki-67-labeled nuclei. We studied five melanocytic skin tumors. From each case, five parallel sections were prepared and stained using the peroxidase-antiperoxidase (PAP) technique (slide 1) and the APAAP technique once (slide 2). Slide 3 consisted of a single repetition of the APAAP technique, slide 4 was a double repetition, and slide 5 was a third repetition. We assessed the volume fraction (VV) of Ki-67-positive nuclei using computer-assisted image analysis. For each staining group, the mean value and standard deviation of VV were calculated. Comparing VV values obtained from the different staining groups we did not find a statistically significant difference between the IP and the various APAAP steps (Wilcoxon test, p = less than 0.05). However, the staining procedure influenced the quantitative results to some extent. The mean VV of the five staining groups ranged in our study from 0.10 to 0.17%, which is narrow compared with the overall variability among different cases (dermal melanocytic nevus, 0.01%; metastatic malignant melanoma, 0.43%). Therefore, we can state that for a rough evaluation of Ki-67-positive nuclei, the influence of different staining methods is negligible; for a subtle quantitative analysis, however, it would nevertheless be preferable to always apply the same staining technique.
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PMID:The influence of staining procedures on the assessment of cell proliferation as defined by the monoclonal antibody Ki-67. 170 Aug 83


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