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C Miyake

Publications and source records attributed to C Miyake.

At least 19 recordsLinked to original sources
PubMed2001

Citrulline, a novel compatible solute in drought-tolerant wild watermelon leaves, is an efficient hydroxyl radical scavenger.

Drought-tolerant wild watermelon accumulates high levels of citrulline in the leaves in response to drought conditions. In this work, the hydroxyl radical-scavenging activity of citrulline was investigated in vitro. The second-order rate constant for the reaction between citrulline and hydroxyl radicals was found to be 3.9x10(9) M(-1) s(-1), demonstrating that citrulline is one of the most efficient scavengers among compatible solutes examined so far. Moreover, citrulline effectively protected DNA and an enzyme from oxidative injuries. Liquid chromatography-mass spectrometry analysis revealed that at least four major products were formed by the reaction between citrulline and hydroxyl radicals. Activities of metabolic enzymes were not inhibited by up to 600 mM citrulline, indicating that citrulline does not interfere with cellular metabolism. We reasoned, from these results, that citrulline contributes to oxidative stress tolerance under drought conditions as a novel hydroxyl radical scavenger.

Citrulline↗
PubMed2001

Crystallization and preliminary X-ray diffraction analysis of glutathione-dependent dehydroascorbate reductase from spinach chloroplasts.

Glutathione-dependent dehydroascorbate reductase (GSH-DHAR) catalyzes the reduction of dehydroascorbate to ascorbate using reduced glutathione as the electron donor. GSH-DHAR from spinach chloroplasts produced in Escherichia coli was crystallized by the hanging-drop vapour-diffusion method. The crystals were monoclinic, space group C2, with unit-cell parameters a = 98.25, b = 39.96, c = 106.86 A, beta = 110.46 degrees. The asymmetric unit contained two molecules, giving a crystal volume per enzyme mass (V(M)) of 2.06 A(3) Da(-1) and a solvent content of 40.3%. A full set of X-ray diffraction data were collected to 2.2 A Bragg spacing from three native crystals with an overall R(merge) of 6.5% and a completeness of 93.4%.

Chloroplasts↗
PubMed2001

Characterization of ascorbate peroxidases from unicellular red alga Galdieria partita.

Galdieria partita, a unicellular red alga isolated from acidic hot springs and tolerant to sulfur dioxide, has at least two ascorbate peroxidase (APX) isozymes. This was the first report to demonstrate that two isozymes of APX are found in algal cells. Two isozymes were separated from each other at the hydrophobic chromatography step of purification and named APX-A and APX-B after the elution order in the chromatography. APX-B accounted for 85% of the total activity. Both isozymes were purified. APXs from Galdieria were monomers whose molecular weights were about 28,000, similar to stromal APX of higher plants. APX-A cross-reacted with monoclonal antibody raised against APX of Euglena gracilis in immunoblotting, but APX-B did not, although the antibody can recognize all other APXs tested. The amino-terminal sequences of APX-A and -B from Galdieria had some homology with each other but little homology with those from other sources. Their Km values for ascorbate and hydrogen peroxide were comparable with those of APX from higher plants. Unlike the green algal enzymes, the donor specificities of Galdieria APXs were as high as those of plant chloroplastic APX. On the contrary, these APXs reduced tertiary-butyl hydroperoxide as an electron acceptor as APXs from Euglena and freshwater Chlamydomonas do. The inhibition of APX-A and -B by cyanide and azide, and characteristics of their light absorbance spectra indicated that they were heme peroxidases.

Amino Acid Sequence↗
PubMed2001

Cyclic flow of electrons within PSII in thylakoid membranes.

In photosynthesis, the electrons released from PSII are considered to be shared mainly by carbon metabolism and the water-water cycle. We demonstrated previously that some electrons are utilized in a CO2- and O2-independent manner in leaves of wild watermelon [Miyake and Yokota (2000) Plant Cell Physiol: 41: 335]. In the present study, we examined the mechanism of this alternative flow of electrons in thylakoid membranes, isolated from fresh spinach leaves, by simultaneously measuring the quantum yield of PSII and the flux of the linear flow of electrons. In the presence of the protonophore nigericin, which eliminates the pH gradient across thylakoid membranes, the quantum yield and the flux of the linear flow of electrons were directly proportional to one another. The quantum yield at a given linear flux of electrons was much higher in the absence of nigericin than in its presence, indicating that an additional or alternative flow of electrons can occur independently of the linear flow in the absence of nigericin. In the presence of nigericin, the alternative flux of electrons increased with decreasing pH and with increasing reduction of the plastoquinone pool. Cyclic flow of electrons in PSII appears to be the most plausible candidate for the alternative flow of electrons. The flux reached 280 micromol x e(-) (mg Chl)(-1) x h(-1) and was similar to that of the CO2- and O2-independent alternative flow of electrons that we found in leaves of wild watermelon. The cyclic, alternative flow of electrons in PSII provides a possible explanation for the alternative flow of electrons observed in vivo.

Carbon Dioxide↗
PubMed2000

Chloroplast development in Arabidopsis thaliana requires the nuclear-encoded transcription factor sigma B.

Development of plastids into chloroplasts, the organelles of photosynthesis, is triggered by light. However, little is known of the factors involved in the complex coordination of light-induced plastid gene expression, which must be directed by both nuclear and plastid genomes. We have isolated an Arabidopsis mutant, abc1, with impaired chloroplast development, which results in a pale green leaf phenotype. The mutated nuclear gene encodes a sigma factor, SigB, presumably for the eubacterial-like plastid RNA polymerase. Our results provide direct evidence that a nuclear-derived prokaryotic-like SigB protein, plays a critical role in the coordination of the two genomes for chloroplast development.

Arabidopsis↗
PubMed2000

Formate protects photosynthetic machinery from photoinhibition.

In plants, environmental adversity often leads to the formation of reactive oxygen species (ROS) because of excess light energy. We found that incubation of rice leaves under high light intensity together with CO2-depleted air seriously damaged photosynthesis; however, the application of potassium formate (2 mM) before the photoinhibitory treatment protected the photosynthesis of the plant from photoinhibition. Further analysis revealed that formate protects PSII, RuBisCO, and FBPase from photoinhibition. Formate is thought to be involved in endogenous radical scavenging and/or in the supply of CO2, derived from the formate, thereby reducing oxidative damage to the photosystems under photoinhibitory conditions.

Journal Article↗
PubMed2000

Determination of the rate of photoreduction of O2 in the water-water cycle in watermelon leaves and enhancement of the rate by limitation of photosynthesis.

A study was performed to determine how the electron fluxes for the photosynthetic carbon reduction (PCR) and the photorespiratory carbon oxidation (PCO) cycles affect the photoreduction of O2 at PSI, which is the limiting step in the water-water cycle. Simultaneous measurements were made of CO2-gas exchange, transpiration and quantum yield of PSII [phi(PSII)] using leaves of watermelon (Citrullus lanatus). The total electron flux in PSII[Je(PSII)], as estimated from phi(PSII), was always larger than the total electron flux required for the PCR and PCO cycles at various partial pressures of CO2 and O2 and 1,100 micromol photons m(-2)s(-1). This observation suggested the existence of an alternative electron flux (Ja). Ja was divided into O2-dependent [Ja(O2-depend)] and O2-independent [Ja(O2-independ)] components. The magnitude of half Ja(O2-depend), 7.5 to 9.5 micromol e- m(-2)s(-1), and its apparent Km for O2, about 8.0 kPa, could be accounted for by the photoreduction of O2 at PSI either mediated by ferredoxin or catalyzed by monodehydroascorbate reductase. The results indicated that Ja(O2-depend) was driven by the water-water cycle. A decrease in the intercellular partial pressure of CO2 from 23 to 5.0 Pa at 21 kPa O2 enhanced Ja(O2-depend) by a factor of 1.3. Saturation of the activities of both the PCR and PCO cycles by increasing the photon flux density induced Ja. These results indicate the electron flux in PSII that exceeds the flux required for the PCR and PCO cycles induces the photoreduction of O2 in the water-water cycle.

Carbon Dioxide↗
PubMed2000

Responses of wild watermelon to drought stress: accumulation of an ArgE homologue and citrulline in leaves during water deficits.

Wild watermelon from the Botswana desert had an ability to survive under severe drought conditions by maintaining its water status (water content and water potential). In the analysis by two-dimensional electrophoresis of leaf proteins, seven spots were newly induced after watering stopped. One with the molecular mass of 40 kilodaltons of the spots was accumulated abundantly. The cDNA encoding for the protein was cloned based on its amino-terminal sequence and the amino acid sequence deduced from the determined nucleotide sequences of the cDNA exhibited homology to the enzymes belong to the ArgE/DapE/Acy1/Cpg2/YscS protein family (including acetylornithine deacetylase, carboxypeptidase and aminoacylase-1). This suggests that the protein is involved in the release of free amino acid by hydrolyzing a peptidic bond. As the drought stress progressed, citrulline became one of the major components in the total free amino acids. Eight days after withholding watering, although the lower leaves wilted significantly, the upper leaves still maintained their water status and the content of citrulline reached about 50% in the total free amino acids. The accumulation of citrulline during the drought stress in wild watermelon is an unique phenomenon in C3-plants. These results suggest that the drought tolerance of wild watermelon is related to (1) the maintenance of the water status and (2) a metabolic change to accumulate citrulline.

Amidohydrolases↗
PubMed2000

Purification and characterization of chloroplast dehydroascorbate reductase from spinach leaves.

Green leaves of plants require the high-level activity that can regenerate ascorbate during photosynthesis. One of such enzyme is dehydroascorbate reductase (DHAR), but the molecular and enzymological properties of the enzyme remain to be fully characterized. In this study, we showed that two major DHAR existed in spinach leaves. The two DHARs occupied at least over 90% of total DHAR activity. The amount of the two DHARs was almost the same. We purified both DHARs from spinach leaves. One form of DHAR originated in chloroplasts; the other occurred in the subcellular compartment other than chloroplasts. The chloroplast DHAR had Km values of 70 microM and 1.1 mM for dehydroascorbate and reduced glutathione, respectively. The specific activity of the purified enzyme corresponded to 360 micromol of ascorbate formed per milligram of protein per minute. These properties were quite different from those of trypsin inhibitor, which has been reported to be the plastid DHAR. The other DHAR had the very similar properties to those of chloroplast DHAR. Chloroplast and the other DHARs functioned as a monomer with molecular masses of 26 kDa and 25 kDa, respectively. cDNA for the chloroplast DHAR was cloned with the determined amino-terminal amino acid sequence. The primary sequence predicted from the cDNA included the plastid-targeting sequence. Finally, the significance of chloroplast DHAR in the regeneration of ascorbate is discussed.

Amino Acid Sequence↗
PubMed2000

Aromatic monoamine-induced immediate oxidative burst leading to an increase in cytosolic Ca2+ concentration in tobacco suspension culture.

Aromatic monoamines may contribute to both chemical and physical protection of plants. Addition of phenylethylamine (PEA) and benzylamine to tobacco suspension culture (cell line BY-2) induced a very rapid and transient generation of two active oxygen species (AOS), H2O2 and superoxide anion, both detected with chemiluminescence. Electron spin resonance spectroscopy revealed that hydroxy radicals are also produced. With laser-scanning confocal microscopy, fluorescence spectroscopy and microplate fluorescence reading, intracellular H2O2 production was detected using dichlorofluorescin diacetate as a fluorescent probe. Following AOS production, cytosolic Ca2+ concentration ([Ca2+]c) of the tobacco cells, monitored with luminescence of transgenic aequorin, increased and attained to a peak level 12 s after PEA addition. The PEA-induced increase in [Ca2+]c was inhibited by a Ca2+ chelator, Ca2+ antagonists and AOS scavengers, suggesting that PEA-induced AOS triggered a Ca2+ influx across the plasma membrane.

Amines↗
PubMed2000

Phenylethylamine-induced generation of reactive oxygen species and ascorbate free radicals in tobacco suspension culture: mechanism for oxidative burst mediating Ca2+ influx.

In the previous paper [Kawano et al. (2000a) Plant Cell Physiol. 41: 1251], we demonstrated that addition of phenylethylamine (PEA) and benzylamine can induce an immediate and transient burst of active oxygen species (AOS) in tobacco suspension culture. Detected AOS include H2O2, superoxide anion and hydroxyl radicals. Use of several inhibitors suggested the presence of monoamine oxidase-like H2O2-generating activity in the cellular soluble fraction. It was also suggested that peroxidase(s) or copper amine oxidase(s) are involved in the extracellular superoxide production as a consequence of H2O2 production. Since more than 85% of the PEA-dependent AOS generating activity was localized in the extracellular space (extracellular fluid + cell wall), extracellularly secreted enzymes, probably peroxidases, may largely contribute to the oxidative burst induced by PEA. The PEA-induced AOS generation was also observed in the horseradish peroxidase (HRP) reaction mixture, supporting the hypothesis that peroxidases catalyze the oxidation of PEA leading to AOS generation. In addition to AOS production, we observed that PEA induced an increase in monodehydroascorbate radicals (MDA) in the cell suspension culture and in HRP reaction mixture using electron spin resonance spectroscopy and the newly invented MDA reductase-coupled method. Here we report that MDA production is an indicator of peroxidase-mediated generation of PEA radical species in tobacco suspension culture.

Amines↗
PubMed1999

Crystal structure of carboxylase reaction-oriented ribulose 1, 5-bisphosphate carboxylase/oxygenase from a thermophilic red alga, Galdieria partita.

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1. 39) obtained from a thermophilic red alga Galdieria partita has the highest specificity factor of 238 among the Rubiscos hitherto reported. Crystal structure of activated Rubisco from G. partita complexed with the reaction intermediate analogue, 2-carboxyarabinitol 1,5-bisphosphate (2-CABP) has been determined at 2.4-A resolution. Compared with other Rubiscos, different amino residues bring the structural differences in active site, which are marked around the binding sites of P-2 phosphate of 2-CABP. Especially, side chains of His-327 and Arg-295 show the significant differences from those of spinach Rubisco. Moreover, the side chains of Asn-123 and His-294 which are reported to bind the substrate, ribulose 1,5-bisphosphate, form hydrogen bonds characteristic of Galdieria Rubisco. Small subunits of Galdieria Rubisco have more than 30 extra amino acid residues on the C terminus, which make up a hairpin-loop structure to form many interactions with the neighboring small subunits. When the structures of Galdieria and spinach Rubiscos are superimposed, the hairpin region of the neighboring small subunit in Galdieria enzyme and apical portion of insertion residues 52-63 characteristic of small subunits in higher plant enzymes are almost overlapped to each other.

Algal Proteins↗
PubMed1999

Thioredoxin peroxidase in the Cyanobacterium Synechocystis sp. PCC 6803.

The amino acid sequence deduced from the open reading frame designated sll0755 in Synechocystis sp. PCC 6803 is similar to the amino acid sequences of thioredoxin peroxidases from other organisms. In the present study, we found that a recombinant SLL0755 protein that was expressed in Escherichia coli was able to reduce H2O2 and tertiary butyl hydroperoxide with thioredoxin from E. coli as the electron donor. Targeted disruption of open reading frame sll0755 in Synechocystis sp. PCC 6803 cells completely eliminated the H2O2-dependent and tertiary butyl hydroperoxide-dependent photosynthetic evolution of oxygen and the electron flow in photosystem II. These results indicate that the product of open reading frame sll0755 is a thioredoxin peroxidase whose activities are coupled to the photosynthetic electron transport system in Synechocystis sp. PCC 6803.

Amino Acid Sequence↗
PubMed1998

Purification and molecular properties of ascorbate peroxidase from bovine eye.

Ascorbate peroxidase (APX) is a hydrogen peroxide-scavenging peroxidase which uses ascorbate (AsA) as the specific electron donor. APX has not been isolated in mammals. Ocular tissue contains AsA at high concentrations, and we detected APX activity in bovine retinal pigment epithelium (RPE) and choroid. We purified APX from bovine RPE and choroid by four chromatographic steps. The purified APX was a monomeric hemoprotein with a molecular mass of 43 kDa. The amino acid sequence of the amino-terminal region of the purified APX showed a high degree of homology to that of plants. The primary product of the APX reaction was identified as the monodehydroascorbate radical. The APX showed high specificity for AsA as an electron donor. This is the first isolation and characterization of APX from mammals, and its role in the protection against active species of oxygen in ocular tissue is discussed.

Amino Acid Sequence↗
PubMed1995

Molecular characterization of monodehydroascorbate radical reductase from cucumber highly expressed in Escherichia coli.

Monodehydroascorbate radical (MDA) reductase, an FAD-enzyme, is the first enzyme to be identified whose substrate is an organic radical and catalyzes the reduction of MDA to ascorbate by NAD(P)H. Its cDNA has been cloned from cucumber seedlings (Sano, S., and Asada, K. (1994) Plant Cell Physiol. 35, 425-437), and a plasmid was constructed in the present study that allowed a high level expression in Escherichia coli of the cDNA-encoding MDA reductase using the T7 RNA polymerase expression system. The recombinant MDA reductase was purified to a crystalline state, with a yield of over 20 mg/liter of culture, and it exhibited spectroscopic properties of the FAD similar to those of the enzyme purified from cucumber fruits during redox reactions with NADH and MDA. The red semiquinone of the FAD of MDA reductase was generated by photoreduction. p-Chloromercuribenzoate inhibited the reduction of the enzyme-FAD by NADH, and dicumarol suppressed electron transfer from the reduced enzyme to MDA. The specificity of electron acceptors of the recombinant enzyme appeared to be similar to that of MDA reductase, even though the amino acid sequence encoded by the cDNA was somewhat different from that of the enzyme purified from cucumber fruits. The Km values for NADH and NADPH of the recombinant enzyme indicated a high affinity of the enzyme for NADH. The reaction catalyzed by the enzyme did not exhibit saturation kinetics with MDA up to 3 microM. A second order rate constant for the reduction of the enzyme-FAD with NADH was 1.25 x 10(8) M-1 s-1, as determined by a stopped-flow method, and its value decreased with increases in ionic strength, an indication of the enhanced electrostatic guidance of NADH to the enzyme-FAD.

Cloning, Molecular↗
PubMed1991

Internal jugular vein cannulation: time required under ultrasonographic guidance with a valsalva maneuver.

Time required for the cannulation of right internal jugular vein (IJV) under ultrasonographic guidance with a Valsalva maneuver was investigated in surgical patients. The degree of distension of the IJV and the changes in blood pressure (BP) during the maneuver were also examined. The required time for the cannulation was 11 +/- 5 sec (mean +/- SD, n = 21), and there was no failure in the cannulation. The mean BP decreased significantly during the maneuver, while the vessels enlarged approximately twofold, which facilitated the cannulation. The decrease in BP and the enlargement of the vessels during a Valsalva maneuver were confirmed in the left side, which indicated the feasibility of left IJV cannulation under ultrasonographic guidance.

Journal Article↗