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At least 19 recordsLinked to original sources

PubMed1981

Thioredoxin/Glutaredoxin System of Chlorella: CHLORELLA ADENOSINE 5'-PHOSPHOSULFATE SULFOTRANSFERASE CANNOT USE THIOREDOXIN OR GLUTAREDOXIN AS COFACTORS.

Using the thioredoxin/glutaredoxin-dependent adenosine 3'-phosphate 5'-phosphosulfate reductase coupled assay system, the Chlorella thioredoxin/glutaredoxin system has been partially purified and characterized. A NADPH-thioredoxin reductase and two thioredoxin/glutaredoxin activities, designated as Chlorella thioredoxin/glutaredoxin protein I and II (CPI and CPII), were found in crude extracts of Chlorella. Similar to their counterparts from Escherichia coli, both CPI and CPII are heat-stable low molecular proteins of approximately 14,000. While CPI (but not CPII) is a substrate for its homologous NADPH-thioredoxin reductase as well as for E. coli NADPH-thioredoxin reductase, CPII is better than CPI as a substrate for reduction by the glutathione system. Based on these properties, CPI and CPII may be classified as Chlorella thioredoxin and Chlorella glutaredoxin, respectively. The Chlorella NADPH-thioredoxin reductase (M(r) = 72,000, with two 36,000-dalton subunits) resembles E. coli-thioredoxin reductase in size. Besides Chlorella thioredoxin, the Chlorella thioredoxin reductase will also use E. coli thioredoxin, but not glutaredoxin, as a substrate. Although a thioredoxin-like protein has been implicated in higher plant light-dependent sulfate reaction, neither Chlorella thioredoxin nor glutaredoxin can stimulate the thiol-dependent adenosine 5'-phosphosulfate-sulfotransferase reaction. Furthermore, Chlorella thioredoxin and glutaredoxin, in conjunction with an appropriate reductase system, cannot replace the thiol requirement of Chlorella adenosine 5'-phosphosulfate-sulfotransferase. The exact physiological roles and subcellular localization of the Chlorella thioredoxin and glutaredoxin systems remain to be determined.

Journal Article↗

PubMed2005

Chlorella virus Marburg topoisomerase II: high DNA cleavage activity as a characteristic of Chlorella virus type II enzymes.

Although the formation of a covalent enzyme-cleaved DNA complex is a prerequisite for the essential functions of topoisomerase II, this reaction intermediate has the potential to destabilize the genome. Consequently, all known eukaryotic type II enzymes maintain this complex at a low steady-state level. Recently, however, a novel topoisomerase II was discovered in Paramecium bursaria chlorella virus-1 (PBCV-1) that has an exceptionally high DNA cleavage activity [Fortune et al. (2001) J. Biol. Chem. 276, 24401-24408]. If robust DNA cleavage is critical to the physiological functions of chlorella virus topoisomerase II, then this remarkable characteristic should be conserved throughout the viral family. Therefore, topoisomerase II from Chlorella virus Marburg-1 (CVM-1), a distant family member, was expressed in yeast, isolated, and characterized. CVM-1 topoisomerase II is 1058 amino acids in length, making it the smallest known type II enzyme. The viral topoisomerase II displayed a high DNA strand passage activity and a DNA cleavage activity that was approximately 50-fold greater than that of human topoisomerase IIalpha. High DNA cleavage appeared to result from a greater rate of scission rather than promiscuous DNA site utilization, inordinately tight DNA binding, or diminished religation rates. Despite the fact that CVM-1 and PBCV-1 topoisomerase II share approximately 67% amino acid sequence identity, the two enzymes displayed clear differences in their DNA cleavage specificity/site utilization. These findings suggest that robust DNA cleavage is intrinsic to the viral enzyme and imply that chlorella virus topoisomerase II plays a physiological role beyond the control of DNA topology.

Amino Acid Sequence↗

PubMed2005

Preliminary study of the green algae chlorella (Chlorella vulgaris) for control on the root-knot nematode (Meloidogyne arenaria) in tomato plants and ectoparasite Xiphinema indexin grape seedlings.

The alternative ecological methods require investigation of many organo-biological means for plant protection against dangerous root parasites such as root-knot nematode Meloidogyne arenaria and some ectoparasites (Xiphinema index). The Bulgarian organic product - dry extract of green alga Chlorella vulgaris ("The Golden Apple"-Plamen Barakov) is the latest product, which in comparative aspect gives the best results. Series of laboratory and pot experiments are carried out with tomato (cv. Bele and cv. Ideal) and grape seedlings (cv. Cabernet Sauvignon). Different dosages of Chlorella from 0.5 g to 2 g per plant/pot are investigated. The first results show that even low dosages had double effect - on the one hand they suppress the parasite development and on the other hand they strongly stimulate plant growing. The very important conclusion is that Chlorella vulgaris ignores the negative influence of M. arenaria and X. index. These results give us opportunity for future model and field investigations of Chlorella vulgaris with the aim of its practical application.

Animals↗

PubMed1995

Photosynthetic Shutdown in Chlorella NC64A Associated with the Infection Cycle of Paramecium bursaria Chlorella Virus-1.

The effects of the algal virus Paramecium bursaria Chlorella virus-1 on the photosynthetic physiology of its host, Chlorella NC64A, was studied by observing changes in Chl fluorescence quenching and O2 exchange. Metabolic changes were calibrated against electron microscopic analysis of the morphological changes that occur during the infection cycle. It takes approximately 10 h from attachment of the virus to final lysis of the host cell, so a complete infection cycle can be observed continuously in one experiment. During the early stages of the infection cycle many rapid changes occurred in the host cell's metabolism and these were reflected in changes of photosynthetic and respiratory rates. The dramatic inhibition of photosynthesis in Chlorella NC64A cells by P. bursaria Chlorella virus-1 has facilitated the use of fluorescence quenching as an accurate measure of the first phase of viral infection (attachment and penetration of the host cell) and the extent to which a population of host cells is infected. Effects of temperature and cation requirement of the infection cycle are described. The relevance of our observations to the events observed during viral infection of higher plants is discussed.

Journal Article↗

PubMed2005

Maternal-fetal distribution and transfer of dioxins in pregnant women in Japan, and attempts to reduce maternal transfer with Chlorella (Chlorella pyrenoidosa) supplements.

Dioxins can be transferred from mother to fetus via the placenta, or to nursing infants via breast milk, potentially causing developmental health problems in children. To assess pediatric health risks from dioxins, exposure of mothers and children to dioxins must be clarified. Methods of reducing maternal transfer of dioxins should also be investigated. Concentrations of 28 dioxin (polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and co-planar polychlorinated biphenyls) congeners in blood, adipose tissue, breast milk, cord blood and placenta collected from 44 pregnant Japanese women were measured. In addition, to investigate potential reductions in maternal transfer of dioxins, 23 pregnant women were instructed to take Chlorella pyrenoidosa supplements during pregnancy. Correlations were observed between dioxin total toxic equivalents (total TEQ) in blood and total TEQ in adipose tissue (r=0.913, P<0.0001), breast milk (r=0.695, P=0.0007), and cord blood (r=0.759, P<0.0001). Dioxin levels transferred to fetuses and nursing infants reflect cumulative maternal concentrations of dioxins. A linear regression equation was introduced to predict total TEQ in breast milk and cord blood from dioxin levels in maternal blood, which should prove useful in evaluating fetal and infant risk of dioxin exposure. Total TEQ in cord blood were approximately 26% lower than in maternal blood (P<0.0001). The results of this study suggest that transplacental transfer differs depending on the dioxin congener. Total TEQ in breast milk were approximately 30% lower in the Chlorella group than in controls (P=0.0113). This finding suggests that maternal transfer of dioxins can be reduced using dietary measures such as Chlorella supplements.

Adipose Tissue↗

PubMed1976

[Glutamine metabolism regulation in Chlorella pyrenoidosa. Regulation of Chlorella glutamine synthetase activity by amino acids].

Effect of glutamine and its metabolites (amino acids) on Chlorella glutamine synthetase (GS) (E.C.6.3.1.2) in the presence of Mg or Mn was studied. Purified GS preparation was used, isolated from Chlorella grown in the presence of NH as a sole nitrogen source. Glutamate, aspartate, alanine and glycine inhibit GS activity in the presence of both Mg and Mn. Tryptophane and valine (up to 15 mM) activate GS in the presence of Mn. Tryptophane inhibits GS in the system with Mg. Sinergistic inhibition was observed under the combined effect of amino acids on GS in the presence of Mn and aspartate or alanine. The change of GS activity observed is supposed to be due to the inhibitory effect of glutamine and amino acids studied, since the glutamine content is increased (in 2.5 times for 5 min) and that of alanine and dicarbonic amino acids (for the following 15 min) under NH assimilation in Chlorella cells.

Amino Acids↗

PubMed1989

Pyrroline-5-Carboxylate Reductase in Chlorella autotrophica and Chlorella saccharophila in Relation to Osmoregulation.

Pyrroline-5-carboxylate (P5C) reductase (EC 1.5.1.2), which catalyzes the reduction of P5C to proline, was partially purified from two Chlorella species; Chlorella autotrophica, a euryhaline marine alga that responds to increases in salinity by accumulating proline and ions, and Chlorella saccharophila, which does not accumulate proline for osmoregulation. From the elution profile of this enzyme from an anion exchange column in Tris-HCl buffer (pH 7.6), containing sorbitol and glycine betaine, it was shown that P5C reductase from C. autotrophica was a neutral protein whereas the enzyme from C. saccharophila was negatively charged. The kinetic mechanisms of the reductase was characteristic of a ping-pong mechanism with double competitive substrate inhibition. Both enzymes showed high specificity for NADH as cofactor. The affinities of the reductases for their substrates did not change when the cells were grown at different salinities. In both algae, the apparent K(m) values of the reductase for P5C and NADH were 0.17 and 0.10 millimolar, respectively. A fourfold increase in maximal velocity of the reductase was observed when C. autotrophica was transferred from 50 to 150% artificial sea water. Even though the reductase was inhibited by NaCl, KCl, and proline, it still showed appreciable activity in the presence of these compounds at molar concentrations. A possible role for the regulation of proline synthesis at the step catalyzed by P5C reductase is discussed in relation to the specificity of P5C reductase for NADH and its responses to salt treatments.

Journal Article↗

PubMed1979

Experiments on the accumulation of lindane (gamma-BHC) by the primary producers Chlorella spec. and Chlorella pyrenoidosa.

Experiments were performed on the accumulation of the pesticide lindane (gamma-isomer of BHC) by two algae with different surfaces. An analytical procedure was developed for the gas chromatographic determinnation of lindane. At room temperature, lindane had a water solubility of 7.8 mg/L in distilled water and 6.7 mg/L in tap water. Under the experimental conditions of 10 to 100 microgram/L, 2.3% of the dissolved lindane was lost through adsorption on the glass walls of the equipment and 0.2% through evaporation. The recovery rate of lindane was 98% for the water samples and more than 90% for Chlorella spec. The tolerance in the gas chromatographic measurements amounted to 1.2%. Investigations on the effect of lindane on the growth of Chlorella spec. revealed irreparable damage to the algae cells through loss of chlorophyll, coagulation, and complete sedimentation at concentrations greater than 300 microgram/L. The experiments on sublethal accumulation showed the development of a state of equilibrium between the amount of lindane per cell and in the surrounding water with lindane concentrations of 10 to 100 microgram/L. The lindane was adsorptively attached to the algal cells within a few hr, and after three days lindane stabilized in the cells. The gelatinous surface of the algae increases the accumulation of lindane.

Chlorella↗

PubMed1984

Detoxification of chlordecone poisoned rats with chlorella and chlorella derived sporopollenin.

Chlorella protothecoides accelerated the detoxification of chlordecone poisoned rats, decreasing the half-life of the toxin from 40 to 19 days. The ingested algae passed through the gastrointestinal tract unharmed , interrupted the enteric recirculation of the persistent insecticide, and subsequently eliminated the bound chlordecone with the feces. The detoxification was similar to that obtained with cholestyramine. Laboratory preparations were made to determine whether cell-free components retained the therapeutic properties of the whole cells. Acid and alkaline hydrolysis of the algae destroyed the cells except for the resistant cell wall components. One component was sporopollenin , a carotenoid polymer of limited natural occurrence among microorganisms and plants. Plant sporopollenin was not active, but algal cell walls and sporopollenin retained the therapeutic activity of the whole cells. The cells and cell walls have potential as detoxifying drugs for animals poisoned by chlordecone and other xenobiotic compounds with similar properties.

Animals↗

PubMedDate not supplied

[Absorption of radiocobalt in Chlorella vulgaris]?1Assorbimento di radiocobalto in "Chlorella vulgaris".

The uptake, accumulation and loss of traces of radiocobalt present in the culture medium by a green alga, Chlorella vulgaris, were studied. The trace quantities of the radionuclide employed had no effect on the growth of the algal population. The uptake is related to the number of cells present and to the temperature of the culture medium; it is not affected by mitotic activity. The rate of the 60Co, uptake during algal growth is compared to the rate of uptake of other radioisotopes; 90Sr and, to some extent, 137Cs have the same rate of uptake as 60Co, whereas 90Y and 144Ce differ. Perhaps the radiocobalt in the cells undergoes a chelating process and consequently its loss to the outer environment is very slow. The involvement of a biological process, in addition to a physical one, is claimed in order to explain the possibility of an active concentration of the radioisotope (C.F.=170). Emphasis is laid on the possible danger of this concentration when a disposal system by dilution of industrial or nuclear waste is employed.

Cesium Radioisotopes↗

PubMed1963