Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Four manned experiments (4 test subjects participating in each) were carried out in a chamber of 24 m3. The effect of CO at a concentration of 10 to 45 mg/m3 on the content of carboxyhemoglobin in the blood, nonhemoglobin iron in the plasma, CO in the breathing air, catalase and peroxidase activity was studied. A correlation was found between these parameters and CO concentration in the atmosphere and exposure time. It was demonstrated that a continuous exposure (up to 90 days) to CO at a concentration of 10 mg/m3 under favorable microclimatic conditions produced no significant effect on the above mentioned biochemical paramters.
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PMID:[Relationship of the content of carboxyhemoglobin in the blood and of carbon monoxide in the expired air of test subjects to the CO concentration in the air of a hermetic chamber]. 1 44

1. The steady state kinetics for the oxidation of ferrocytochrome c by yeast cytochrome c peroxidase are biphasic under most conditions. The same biphasic kinetics were observed for yeast iso-1, yeast iso-2, horse, tuna, and cicada cytochromes c. On changing ionic strength, buffer anions, and pH, the apparent Km values for the initial phase (Km1) varied relatively little while the corresponding apparent maximal velocities varied over a much larger range. 2. The highest apparent Vmax1 for horse cytochrome c is attained at relatively low pH (congruent to 6.0) and low ionic strength (congruent to 0.05), while maximal activity for the yeast protein is at higher pH (congruent to 7.0) and higher ionic strength (congruent to 0.2), with some variations depending on the nature of the buffering ions. 3. Direct binding studies showed that cytochrome c binds to two sites on the peroxidase, under conditions that give biphasic kinetics. Under those ionic conditions that yield monophasic kinetics, binding occurred at only one site. At the optimal buffer concentrations for both yeast and horse cytochromes c, the KD1 and KD2 values approximate the Km1 and Km2 values. At ionic strengths below optimal, binding becomes too strong and above optimal, too weak. 4. Under ionic conditions that are optimal and give monophasic kinetics with horse cytochrome c but are suboptimal for the yeast protein, yeast cytochrome c strongly inhibits the reaction of horse cytochrome c with peroxidase, uncompetitively at one site and competitively at a second site. The appearance of the second site under monophasic conditions is interpreted as an allosteric effect of the inhibitor binding to the first site. 5. The simplest model accounting for these observations postulates two kinetically active sites on each molecule of peroxidase, a high affinity and a low affinity site, that may correspond to the free radical and the heme iron (IV) of the oxidized enzyme, respectively. Both oxidizing equivalents may be discharged at either site. Furthermore, the enzyme appears to exist as an equilibrium mixture of a high ionic strength form, EH and a low ionic strength form, EL, the former reacting optimally with yeast cytochrome c, and the latter with horse cytochrome c.
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PMID:Steady state kinetics and binding of eukaryotic cytochromes c with yeast cytochrome c peroxidase. 1 38

The formation of HCN from D-histidine in Chlorella vulgaris extracts is shown to be due to the combined action of a soluble protein and a particulate component. Either horse-radish peroxidase (EC 1.11.1.7) or a metal ion with redox properties can be substituted for the particulate component. Ions of manganese and vanadium are especially effective, as are o-phenanthroline complexes of iron. Cobalt ions are less active. The D-amino acid oxidase (EC 1.4.3.3) from kidney and the L-amino acid oxidase (EC 1.4.3.2) from snake venom likewise cause HCN production from histidine when supplemented with the particulate preparation from Chlorella or with peroxidase or with a redox metal ion. The stereospecificity of the amino acid oxidase determines which of the two stereoisomers of histidine is active as an HCN precursor. Though histidine is the best substrate for HCN production, other naturally occurring aromatic amino acids (viz. tyrosine, phenylalanine and tryptophan) can also serve as HCN precursors with these enzyme systems. The relative effectiveness of each substrate varies with the amino acid oxidase enzyme and with the supplement. With respect to this latter property, the particulate preparation from Chlorella behaves more like a metal ion than like peroxidase.
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PMID:Cyanide formation from histidine in Chlorella. A general reaction of aromatic amino acids catalyzed by amino acid oxidase systems. 1 6

The heme vicinities of the acid and alkaline forms of native (Fd(III)) horseradish peroxidase were investigated in terms of the magnetic circular dichroism (MCD) spectroscopy. The MCD spectrum of the acid form of native horseradish peroxidase was characteristic of a ferric high spin heme group. The resemblance in the MCD spectrum between the acid form and acetato-iron (III)protoporphyrin IX dimethyl ester suggests that the heme iron of the acid form has the electronic structure similar to that in a pentocoordinated heme complex. The MCD spectra of native horseradish peroxidase did not shown any substantial pH dependence in the pH range from 5.20 to 9.00. The MCD spectral change indicated the pK value for the equilibrium between the acid and alkaline forms to be 11.0 which agrees with the results from other methods. The alkaline form of native horseradish peroxidase at pH 12.01 exhibited the MCD spectrum of a low spin complex. The near infrared MCD spectrum suggests that the alkaline form of native horseradish peroxidase has a 6th ligand somehow different from a normal nitrogen ligand such as histidine or lysine. It implicates that the alkaline form has an overall ligand field strength of between the low spin component of metmyoglobin hydroxide and metmyoglobin azide.
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PMID:Magnetic circular dichroism studies on acid and alkaline forms of horseradish peroxidase. 1 85

The magnetic circular dichroism spectra (MCD) recorded for the visible and near-UV regions of high-spin ferrous derivatives of myoglobin, hemoglobin, hemoglobin dimers and isolated chains as well as of horseradish peroxidase at pH 6.8 and 11.4 have been compared at the room and liquid nitrogen temperatures. The MCD of the Q00- and QV-bands have been shown to be sensitive to structural differences in the heme environment of these hemoproteins. The room temperature visible MCD of native hemoglobin differs from that of myoglobin, hemoglobin dimers and isolated chains as well as from that of model pentacoordinated complex. The MCD of hemoglobin is characterized by the greater value of the MCD intensity ratio of derivative shape A-term in the Q00-band to the A-term in the QV-band. The evidneces are presented for the existence of two pH-dependent forms of ferroperoxidase, the neutral peroxidase shows the "hemoglobin-like" MCD, while the alkaline ferroperoxidase is characterized by the "myoglobin-like" MCD spectrum in the visible region. The differences in the MCD of deoxyhemoglobin and neutral ferroperoxidase as compared with other high-spin ferrous hemoproteins are considered to result from the constraints on heme group imposed by quaternary and/or tertiary protein structure. The differences between hemoporteins which are seen at the room temperature become more pronounced at liquid nitrogen temperature. Except the peak at approximately 580 nm in the MCD of deoxymyoglobin and reduced peroxidase at pH 11.4 the visible MCD does not show appreciable temperature dependent C-terms. The nature of the temperature dependent effect at approximately 580 nm is not clear. The Soret MCD of all hemoproteins studied are similar and are predominantly composed of the derivative-shaped C-terms as revealed by the increase of the MCD peaks approximately in accordance with Boltzmann distribution. The interpretation of temperature-dependent MCD observed for the Soret band has been made in terms of porphyrin to Fe-iron charge-transfer electronic transition which may be assigned as b( pi) leads to 3d. This charge-transfer band is strongly overlapped with usual B(pi --pi*) band resulting in diffuse Soret band. Adopting that only two normal vibrations are sinphase with charge-transfer transition the extracted C-terms of the Soret MCD have been fitted by theoretical dispersion curves.
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PMID:Magnetic circular dichroism studies of myoglobin, hemoglobin and peroxidase at room and low temperatures. Ferrous high spin derivatives. 2 82

Differences were seen in the relative importance of spleen and marrow in early erythroid regeneration of lethally irradiated mice given spleen or marrow cell transplants compared with that in sublethally irradiated mice with surviving endogenous hematopoietic cells. Radioactive iron uptake was predominantly in the spleen of mice with transplants and in the marrow of endogenously recovering mice. Visable spleen colony counts increased from day 4 to day 7 and plateaued through day 10 in the transplant system, but shoed a small abortive rise with a 5-day peak, followed by a steady increase from days 6 to 10 in the endogenous system. Comparisons of peroxidase-positive cells (granulocytes) in the marrow of femurs and humeri and iron uptake in marrow and spleen suggested that repopulation of the marrow and spleen were independent, while that of different areas of the marrow was interrelated. The interrelationship of the rate of marrow regeneration was closer in the endogenous than in the transplant system.
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PMID:Lack of correlation between splenic and marrow hematopoiesis following irradiation or irradiation and transplantation in mice. 2 95

220 MHz proton Fourier transform (FT) NMR with quadrature phase detection (QPD) technique is applied to observe largely hyperfine-shifted signals of various hemoproteins and hemoenzymes in ferric high-spin state. The binding of F-, OCN-, SCN-, and CH3OH to the ferric heme iron in high-spin state in various hemoproteins has been studied by the use of FT/QPD technique at 220 MHz. The binding of formate ion to metmyoglobin (metMb) has also been studied. The spectrum of the formate complex was compared with that of hemoglobin M Milwaukee where carboxylate groups are bound to the hemes of the beta subunits. The acid-base transition of ferric myoglobin (Mb) was confirmed by monitoring the pH-dependent shift of the heme side methyl signals with the reflection point at pH 9.1. This finding is analyzed on the basis of rapid exchange between alkaline (low spin) and acidic (high spin) forms accompanied by the dissociation and association of one proton in the ferric Mb. The structure of the heme environment of ferric horseradish peroxidase (HRP) was studied. The pH-dependent features of NMR spectra of the ferric enzyme and its complexes with cyanide and azide were discussed in terms of heme environmental structures, comparing with the case of metMb. The results were interpreted as follows: There exists an ionizable amino group near the heme responsible for the ligand binding reactions of the enzyme, which modulates the entry of external azide to the heme iron through protolytic equilibrium of this group. The pK value of this group was determined to be 5.9 by monitoring the pH-dependent shift of the heme peripheral methyl signals of the native enzyme, indicating that the group is probably a histidyl residue. Acid-alkaline transition of metMb was confirmed to associate with the proton dissociation of an iron-bound water molecule, whereas in HRP, pH-dependent spin state change characterized by pK 11 is attributed not to the simple protolytic reaction of the iron-bound water but to the direct coordination of an amino acid residue of the polypeptide chain to the ferric heme iron. Histidyl imidazole is a possible candidate for the new sixth iron ligand in alkaline peroxidase above pH 11. Interaction of HRP with electron donor(indolepropionic acid, IPA) was also studied. The hyperfine-shifted proton signals of the heme peripheral groups of the enzyme showed a small but significant shift with stepwise additions of IPA, indicating that the donor binds at a specific site of HRP. There results are interpreted in terms of the interaction between the enzyme and the donor at the heme edge site.
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PMID:Nuclear magnetic resonance studies of high-spin ferric hemoproteins. 2 54

The paper confirms the existence of a peroxide mechanism involved in oxidation of iron and manganeses by the most typical iron bacteria growing at neutral acidity of the medium. Oxidation of bivalent iron and manganese is accomplished by the simultaneous action of catalase and hydrogen peroxide produced in the respiratory chain in the course of oxidation of organic substances. Catalase performs the peroxidase function in these processes. The possibility of these biological reactions to occur and the necessary conditions have been studied in vitro. Possible variants of iron and manganese oxidation by iron bacteria are discussed, including the conditions for "symbiotic" oxidation of manganese by mixed cultures of microorganisms.
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PMID:[Mechanism of the oxidation of divalent iron and manganese by iron bacteria developing in a neutral acidic medium]. 3 22

Resonance Raman spectra of the heme protein chloroperoxidase in its native and reduced forms and complexed with various small ions are obtained by using laser excitation in the Soret region (350-450 nm). Additionally, Raman spectra of horseradish peroxidase, cytochrome P-450cam, and cytochrome c, taken with Soret excitation, are presented and discussed. The data support previous findings that indicate a strong analogy between the active site environments of chloroperoxidase and cytochrome P-450cam. The Raman spectra of native chloroperoxidase are found to be sensitive to temperature and imply that a high leads to low spin transition of the heme iron atom takes place as the temperature is lowered. Unusual peak positions are also found for native and reduced chloroperoxidase and indicate a weakening of porphyrin ring bond strengths due to the presence of a strongly electron-donating axial ligand. Enormous selective enhancements of vibrational modes at 1360 and 674 cm-1 are also observed in some low-spin ferrous forms of the enzyme. These vibrational frequencies are assigned to primary normal modes of expansion of the prophyrin macrocycle upon electronic excitation.
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PMID:Resonance Raman investigations of chloroperoxidase, horseradish peroxidase, and cytochrome c using Soret band laser excitation. 3 29

The topography of the active sites of native horseradish peroxidase and manganic horseradish peroxidase has been studied with the aid of a spin-labeled analog of benzhydroxamic acid (N-(1-oxyl-2,2,5,5-tetramethylpyrroline-3-carboxy)-p-aminobenzhydroxamic acid). The optical spectra of complexes between the spin-labeled analog of benzhydroxamic acid and Fe3+ or Mn3+ horseradish peroxidase resembled the spectra of the corresponding enzyme complexes with benzhydroxamic acid. Electron spin resonance (ESR) measurement indicated that at pH 7 the nitroxide moiety of the spin-labeled analog of benzhydroxamic acid became strongly immobilized when this label bound to either ferric or manganic horseradish peroxidase. The titration of horseradish peroxidase with the spin-labeled analog of benzhydroxamic acid revealed a single binding site with association constant Ka approximately 4.7 . 10(5) M-1. Since the interaction of ligands (e.g. F-, CN-) and H2O2 with horseradish peroxidase was found to displace the spin label, it was concluded that the spin label did not indeed bind to the active site of horseradish peroxidase. At alkaline pH values, the high spin iron of native horseradish peroxidase is converted to the low spin form and the binding of the spin-labeled analog of benzhydroxamic acid to horseradish peroxidase is completely inhibited. From the changes in the concentration of both bound and free spin label with pH, the pK value of the acid-alkali transition of horseradish peroxidase was found to be 10.5. The 2Tm value of the bound spin label varied inversely with temperature, reaching a value of 68.25 G at 0 degree C and 46.5 G at 52 degrees C. The dipolar interaction between the iron atom and the free radical accounted for a 12% decrease in the ESR signal intensity of the spin label bound to horseradish peroxidase. From this finding, the minimum distance between the iron atom and nitroxide group and hence a lower limit to the depth of the heme pocket of horseradish peroxidase was estimated to be 22 A.
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PMID:A spin label study of horseradish peroxidase. 4 80


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