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I Yamazaki

Publications and source records attributed to I Yamazaki.

At least 19 recordsLinked to original sources
PubMed1992

Haloperoxidase activity of Phanerochaete chrysosporium lignin peroxidases H2 and H8.

Monochlorodimedone (MCD), commonly used as a halogen acceptor for haloperoxidase assays, was oxidized by hydrogen peroxide in the presence of lignin peroxidase isoenzymes H2 and H8. When oxidized, it produced a weak absorption band with an intensity that varied with pH. This absorbance was used as a simple method for the product analysis because it disappeared when MCD was brominated or chlorinated. We assessed the activity of the lignin peroxidases for oxidation of bromide by measuring the bromination of MCD, the formation of tribromide, the bromide-mediated oxidation of glutathione, and the bromide-mediated catalase-like activity. We analyzed the reaction products of MCD and the halide-mediated oxidation of glutathione when bromide was replaced by chloride. These enzymes demonstrated no significant activity for oxidation of chloride. Unlike other peroxidases, the lignin peroxidases exhibited similar pH-activity curves for the iodide and bromide oxidations. The optimum pH for activity was about 2.5. Surprisingly, this pH dependence of lignin peroxidase activity for the halides was nearly the same in the reactions with hydrogen donors, such as hydroquinone and guaiacol. The results suggested that protonation of the enzymes with pKa approximately 3.2 is necessary for the catalytic function of lignin peroxidases, irrespective of whether the substrates are electron or hydrogen donors. These unique reaction profiles of lignin peroxidases are compared to those of other peroxidases, such as lactoperoxidase, bromoperoxidase, chloroperoxidase, and horseradish peroxidase. Isozyme H2 was more active than isozyme H8, but isozyme H8 was more stable at very acidic pH.

Basidiomycota↗
PubMed1992

Structure of the active site of lignin peroxidase isozyme H2: native enzyme, compound III, and reduced form.

The wood-degrading fungus Phanerochaete chrysosporium secretes a number of extracellular enzymes called lignin peroxidases which are involved in the degradation of both lignin and a number of persistent environmental pollutants. Lignin peroxidase isozyme H2, a glycosylated protein of approximately 40 kDa, contains a single heme. X-ray absorption spectroscopy (XAS) has been used to probe the local environment of the iron in the active site of resting enzyme, reduced enzyme, and compound III. For the native and reduced forms, respectively, the average Fe-pyrrole nitrogen distances are 2.055 and 2.02 A (+/- 0.015 A); the Fe-proximal nitrogen distance is 1.93 and 1.91 A (+/- 0.02 A) while the Fe-distal ligand distance is 2.17 and 2.10 A (+/- 0.03 A). Although the results are not as well-defined, the active-site structure of compound III is largely 2.02 +/- 0.015 A for the average Fe-pyrrole nitrogen distance, 1.90 +/- 0.02 for the Fe-proximal nitrogen, and 1.74 +/- 0.03 A for the Fe-distal ligand distance. The heme iron-pyrrole nitrogen distance is more expanded in ligninase H2 than in other peroxidases. The possible significance of this is discussed in relation to other heme proteins.

Basidiomycota↗
PubMed1992

Inhibitory effect of ipriflavone on pit formation in mouse unfractionated bone cells.

Effects of ipriflavone (7-isopropoxyisoflavone) on osteoclast-induced bone resorption were evaluated using an unfractionated bone cell culture system containing mature osteoclasts from the femur and tibia of newborn mice. When cells were cultured for 4 days on dentin slices in the presence of 5% fetal bovine serum and 10(-8) M 1 alpha, 25(OH)2D3, ipriflavone (3 x 10(-7) -3 x 10(-5) M) inhibited pit formation and caused a decrease in the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs). The lowest significant effect was observed at a concentration of 10(-6) M. Unlike ipriflavone, calcitonin inhibited pit formation 4 days after the culture was started without affecting the number of TRAP-positive MNCs. Ipriflavone still inhibited pit formation when the culture period was 13 days, when new osteoclasts were expected to be formed. These findings suggest that ipriflavone inhibits new osteoclast formation and bone resorption at the cellular level.

Acid Phosphatase↗
PubMed1991

Altered localization of antigen recognized by proteinuria-inducing monoclonal antibody in experimental nephrosis.

Change in the localization of the antigen recognized by the proteinuria-inducing monoclonal antibody (MA) 5-1-6 in experimental nephrosis was studied by indirect and biotin-avidin immunofluorescence, and immunoperoxidase at light and electron microscopical levels. The proteinuric state was induced by the administration of the aminonucleoside of puromycin (PAN) or adriamycin. The antigen decreased in quantity and/or its distribution changed with an increase in the amount of protein excreted in both experimental models. Recovery from the alterations observed during the development and proteinuria appeared to occur when PAN-induced proteinuria subsided. This antigenic molecule may thus be essential for maintaining the normal permselectivity of glomerular capillary walls.

Animals↗
PubMed1990

ESR spin-trapping studies on the reaction of Fe2+ ions with H2O2-reactive species in oxygen toxicity in biology.

Using ESR spin-trapping techniques with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), we confirmed the 1:1 stoichiometry for the formation of hydroxyl radicals with Fe2+ in the Fenton reaction under experimental conditions wherein [H2O2] is 90 microM and [Fe2+] is very low, 1 microM or less. The stoichiometry decreased markedly as the Fe2+ concentration was increased. The efficiency of hydroxyl radical generation varied with the nature of the iron chelators used and increased in the order of phosphate alone approximately ADP less than EDTA less than diethylenetriaminepentaacetic acid (DETAPAC). The second order rate constant for the Fenton reaction was measured to be 2.0 x 10(4) M-1 s-1 for phosphate alone, 8.2 x 10(3) M-1 s-1 for ADP, 1.4 x 10(4) M-1 s-1 for EDTA, and 4.1 x 10(2) M-1 s-1 for DETAPAC. Measuring the radicals formed as spins trapped in the presence of ethanol, we estimated the amount of total oxidizing intermediates formed in the Fenton reaction, which we concluded consists of hydroxyl radicals and an iron species. The oxidizing species of iron which might be assigned as ferryl, FeO2+, or Fe(IV) = O was generated effectively in the presence of ADP even at low Fe2+ concentrations. In general, as the Fe2+ concentration was increased, the ferryl species predominated over the hydroxyl radical except for the case of Fe(II)-DETAPAC, which generated only hydroxyl radicals as the oxidizing species. Three possible pathways are proposed for the Fenton reaction, the dominant ones depending very much on the nature of the iron chelator being used.

Adenosine Diphosphate↗
PubMed1990

Structure and function of the photoreceptor stentorins in Stentor coeruleus. II. Primary photoprocess and picosecond time-resolved fluorescence.

Stentorin serves as the photoreceptor for the photophobic and negative phototactic responses in Stentor coeruleus. Two forms of the stentorin have been isolated and purified. The strongly fluorescent form, stentorin I at pH 7.8, exhibited nearly exponential fluorescence decay monitored at 620 nm, having two comparable lifetime decay components of 2.53 ns (47%) and 5.95 ns (53%). Stentorin I showed no significant time-resolved fluorescence emission spectra in the picosecond-nanosecond time scales. The weakly fluorescent form, stentorin II, exhibited an ultrafast fluorescence decay component (10 ps) at an emission wavelength of 630 nm and pH 7.8. The amplitudes of the multi-component fluorescence in stentorin II were found to be emission wavelength-dependent. Furthermore, the fluorescence emission spectrum was time-resolvable in the picosecond time scales. Effects of pH and pD on the fluorescence decay kinetics and time-resolved spectra of stentorins I and II have also been investigated. Results are suggestive of proton dissociation as a primary photoprocess from the excited state of stentorin II.

Animals↗
PubMed1990

Kinetic studies on spin trapping of superoxide and hydroxyl radicals generated in NADPH-cytochrome P-450 reductase-paraquat systems. Effect of iron chelates.

Electron spin resonance (ESR) studies on spin trapping of superoxide and hydroxyl radicals by 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) were performed in NADPH-cytochrome P-450 reductase-paraquat systems at pH 7.4. Spin adduct concentrations were determined by comparing ESR spectra of the adducts with the ESR spectrum of a stable radical solution. Kinetic analysis in the presence of 100 microM desferrioxamine B (deferoxamine) showed that: 1) the oxidation of 1 mol of NADPH produces 2 mol of superoxide ions, all of which can be trapped by DMPO when extrapolated to infinite concentration; 2) the rate constant for the reaction of superoxide with DMPO was 1.2 M-1 s-1; 3) the superoxide spin adduct of DMPO (DMPO-OOH) decays with a half-life of 66 s and the maximum level of DMPO-OOH formed can be calculated by a simple steady state equation; and 4) 2.8% or less of the DMPO-OOH decay occurs through a reaction producing hydroxyl radicals. In the presence of 100 microM EDTA, 5 microM Fe(III) ions nearly completely inhibited the formation of the hydroxyl radical adduct of DMPO (DMPO-OH) as well as the formation of DMPO-OOH and, when 100 microM hydrogen peroxide was present, produced DMPO-OH exclusively. Fe(III)-EDTA is reduced by superoxide and the competition of superoxide and hydrogen peroxide in the reaction with Fe(II)-EDTA seems to be reflected in the amounts of DMPO-OOH and DMPO-OH detected. These effects of EDTA can be explained from known kinetic data including a rate constant of 6 x 10(4) M-1 s-1 for reduction of DMPO-OOH by Fe(II)-EDTA. The effect of diethylenetriamine pentaacetic acid (DETAPAC) on the formation of DMPO-OOH and DMPO-OH was between deferoxamine and EDTA, and about the same as that of endogenous chelator (phosphate).

Animals↗
PubMed1990

Iodothyronine-induced catalatic activity of thyroid peroxidase.

Iodothyronines induced catalatic (H2O2-decomposing) activity of thyroid peroxidase and lactoperoxidase, the effect increasing in the order of thyroxine (T4) greater than triiodothyronine (T3) greater than diiodothyronine (T2). The iodothyronines served as electron donors in the peroxidase reactions, and during the reactions the catalytic intermediate of thyroid peroxidase was confirmed to be Compound II for T4 and Compound I for T3 and T2 and from the Soret absorption spectra obtained by stopped-flow measurements. Rate constants for the reactions between T4 and Compound II, T3 and Compound I, and T2 and Compound I were estimated at 1.9 x 10(5), 1.3 x 10(6), and 7.1 x 10(5) M-1.s-1, respectively. Unlike the case of thyroid peroxidase, the catalytic intermediate of lactoperoxidase observed during the oxidation of iodothyronines was invariably Compound II. From these and other data it was concluded that thyroid peroxidase catalyzed one-electron oxidation of T4 and two-electron oxidations of T2 and T3 while lactoperoxidase catalyzed exclusively one-electron oxidation of the iodothyronines. Iodide was released during the enzymatic oxidation of iodothyronines, irrespective of the mechanism of one-electron and two-electron oxidations. The amount of released iodide increased in the order of T4 greater than T3 greater than T2. The iodothyronines-induced catalatic activity of these peroxidases was ascribable to the release of iodide, but it was also found that the iodide-enhanced catalatic activity was stimulated by iodothyronines. In this case the effect of iodothyronines was greater in the order of T2 greater than T3 greater than T4, which was consistent with the order of iodothyronine activation for the iodinium cation transfer from enzyme to acceptor.

Animals↗
PubMed1990

[An aorto-coronary bypass graft operation of left coronary ostial stenosis due to aortitis syndrome].

A 24-year-old female with unstable angina due to aortitis syndrome was reported. The coronary-arteriogram in hospital showed 75 percent stenosis of the left coronary ostium. Following two months' steroid therapy for active inflammation, aortocoronary bypass graft was implanted. After the operation. This patient became free from angina attack. Steroid therapy was continued postoperatively as well. The coronary-arteriogram taken seven months after the operation, revealed the patency of the graft.

Adult↗
PubMed1990

The charge-dependent materno-fetal barrier in the rat.

The charge-dependent materno-fetal barrier of near-term rats was examined with two pairs of radiolabelled proteins differently charged. When the proteins were injected intra-arterially, the maternal blood concentrations of the two cationized proteins (BSA and human IgG) exceeded those of native proteins in the chorioallantoic placenta and fetus during the period of examination (15-180 min). In the yolk sac placenta, these percentages were essentially the same as those of native proteins. Following intra-placental injection, the amounts of the cationized proteins in the chorioallantoic placenta and fetus were significantly (p less than 0.01) greater than those of native proteins at the particular times examined (5 and 60 min). In contrast, the amounts of cationized proteins in the yolk sac placenta were basically the same as those of native proteins. The data presented above indicate the charge on proteins that considerably influenced their materno-fetal transfer, particularly via the chorioallantoic placenta.

Animals↗
PubMed1989

Thyroglobulin-mediated one- and two-electron oxidations of glutathione and ascorbate in thyroid peroxidase systems.

The one- or two-electron oxidation of thyroglobulin by the thyroid peroxidase system was found to be regulated by the iodine content of thyroglobulin. The catalytic intermediate of thyroid peroxidase observed at steady state of the reaction was Compound I and II when the iodine content in thyroglobulin was 0.2 and 0.7%, respectively, apparent rate constants for the rate-limiting steps being estimated at 4.7 x 10(7) and 4.8 x 10(4) M-1 S-1. The thyroglobulin-mediated oxidation of GSH occurred by way of two-electron transfer at 0.2% iodine content and by way of one-electron transfer at 0.7% iodine content. The spin-trapping experiment with 5,5-dimethyl-1-pyrroline-N-oxide showed that glutathione radicals were formed in the latter reaction but not in the former. In the reactions of thyroid peroxidase, the one- and two-electron oxidations of ascorbate were also mediated by 0.2 and 0.7% iodine thyroglobulins, respectively. The reactions were analyzed and mimicked with the use of p-cresol and p-acetaminophenol as a mediator in the reactions of lactoperoxidase and thyroid peroxidase.

Acetaminophen↗
PubMed1989

Picosecond-resolved fluorescence spectra of D-amino-acid oxidase. A new fluorescent species of the coenzyme.

Protein dynamics of D-amino-acid oxidase in the picosecond region was investigated by measuring time-resolved fluorescence of the bound coenzyme, FAD. The observed nonexponential fluorescence decay curves were analyzed with four-exponential decay functions. The fluorescence lifetimes at the best fit were 26.6 +/- 0.7 ps, 44.0 +/- 4.2 ps, 177 +/- 11 ps, and 2.28 +/- 0.21 ns at 20 degrees C and 25.2 +/- 3.0 ps, 50.3 +/- 8.7 ps, 228 +/- 27 ps, and 2.75 +/- 0.33 ns at 5 degrees C. Component fractions with the shortest lifetime, ca. 26 ps, were always negative and close to -1. The other fluorescent components of the lifetimes, ca. 47 ps, 200 ps, and 2.6 ns, with positive fractions were assigned to different forms of the enzyme including the dimer, the monomer, and free FAD dissociated from the enzyme. Measurements of the time-resolved fluorescence spectra revealed that the maximum wavelengths of the spectra shifted toward shorter wavelength by 65 nm at 20 degrees C and 36 nm at 5 degrees C within 100 ps after pulsed excitation. The remarkable blue shift was not observed in free FAD. The first spectra immediately after the excitation of the enzyme exhibited maximum wavelengths of 584 nm at 20 degrees C and 557 nm at 5 degrees C. The fluorescence spectra obtained at times later than 100 ps are in good agreement with the one obtained under steady-state excitation of D-amino-acid oxidase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Resonance Raman characterization of hog thyroid peroxidase. An SERRS study.

Resonance Raman (RR) spectra of hog thyroid peroxidase (TPO) were observed for the first time and compared with those of lactoperoxidase (LPO) and horseradish peroxidase (HRP). Since TPO purified by monoclonal antibody-assisted immunoaffinity chromatography was strongly fluorescent, the surface enhancement technique using Ag colloid adsorption was used for the oxidized form, but ordinary RR spectra could be obtained for the reduced form. The RR spectra of TPO were distinct from those of HRP in both the oxidized and reduced states and indicated the presence of six-coordinated iron-protoporphyrin.

Animals↗
PubMed1989

Primary photoprocesses of phytochrome. Picosecond fluorescence kinetics of oat and pea phytochromes.

The primary photoprocesses of etiolated oat and pea phytochromes (Pr forms) are diffusion-modulated by the microscopic viscosity within the chromophore pocket. The chromophore pocket is preferentially accessible to glycerol but not to Ficoll. Glycerol preferentially retarded the rate (rate constant ca. 1-2 X 10(10) s-1) of the initial reaction from the Qy excited state of phytochrome, whereas it increased the long fluorescence lifetime (nanosecond) component that can be attributed to either an emitting intermediate or to modified/conformationally heterogeneous phytochrome populations. The picosecond time-resolved fluorescence spectra of different phytochrome preparations (i.e., full-length vs 6/10-kDa NH2-terminus truncated forms of phytochromes from monocot and dicot plants) revealed no significant differences. The spectra in the picosecond time scale showed no spectral shifts, but at longer time scales of up to approximately 1.90 ns, significant blue spectral shifts were observed. The shifts were more in the truncated than in the full-length pea phytochrome. Comparison of the fluorescence decay data and the picosecond time-resolved fluorescence spectra suggests differences in conformational flexibility/heterogeneity among the preparations of the monocot vs dicot phytochromes and the full-length native vs the amino terminus truncated phytochromes.

Kinetics↗
PubMed1989

Characteristics of an ovariectomized osteopenic rat model.

Although osteoporosis induced by ovariectomy (Ovx) in the rat has been widely used as a model for postmenopausal osteoporosis in humans, the findings of different investigators are not always consistent. This might be mainly due to differences in the age of the animals at Ovx, time after Ovx, and the variables measured. Therefore, in the present study, Ovx was performed at 4, 10, or 52 weeks and bone changes were observed in rats for 6 months. The effects of Ovx on body weight, femoral length, and femoral volume were marked in rats operated on at the age of 4 weeks, slight in rats operated on at the age of 52 weeks, and intermediate in rats operated on at the age of 10 weeks. A reduction in the ratio of cortical thickness to bone width at the midshaft of the femur was observed only in rats ovariectomized at 52 weeks of age. The specific gravity of the femur and the density of the metaphysis of the femur decreased after Ovx in all rats. The ratio of ash weight to dry weight of the femur, a measure of the normal calcification of bone, was unchanged shortly after Ovx but gradually decreased in all rats.

Absorptiometry, Photon↗
PubMed1989

Electron spin resonance spectrum of Tyr-151 free radical formed in reactions of sperm whale metmyoglobin with ethyl hydroperoxide and potassium irridate.

A five-line ESR spectrum was observed at room temperature in reactions of sperm whale metmyoglobin with ethyl hydroperoxide (EtOOH) at pH 9.5 and with potassium irridate at pH's 7.0 and 9.5. A spectrum with the same g value and hyperfine splitting constant appeared in a reaction of sperm whale apomyoglobin with potassium irridate and was assigned to a tyrosyl radical on the basis of optical spectrum data obtained under the same reaction conditions. It was concluded that this radical arose from Tyr-151 for the following reasons. (i) This ESR spectrum could not be observed in the reaction of horse heart metmyoglobin, which lacks Tyr-151. (ii) Sperm whale metmyoglobin no longer gave this spectrum when treated with tetranitromethane (TNM) under conditions in which approximately one tyrosine is lost in sperm whale metmyoglobin but none is lost in horse heart metmyoglobin. (iii) A complex ESR spectrum observed in the reaction of sperm whale metmyoglobin with EtOOH at neutral pH was found to be a mixture of this five-line spectrum and one arising from an unidentified free radical formed in the reaction of horse heart metmyoglobin with EtOOH. The TNM-treated sperm whale metmyoglobin gave the same ESR spectrum as that observed in the reaction of horse heart metmyoglobin with EtOOH.

Animals↗