Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chlorella”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1998

Purification and characterization of ascorbate peroxidase in Chlorella vulgaris.

Chlorella vulgaris contained only one isoform of ascorbate peroxidase (AsAP) as the hydrogen peroxide (H2O2)-scavenging system except for catalase at a specific activity of 3.3 +/- 0.2 units/mg protein. The activity of glutathione peroxidase was not detected in the extracts from cells grown in the absence and presence of sodium selenite. We detected the activity of monodehydroascorbate reductase involved in the regeneration of ascorbate, but we failed to detect the dehydroascorbate reductase activity. AsAP has been purified to electrophoretic homogeneity from Chlorella cells. The enzyme was a monomer with a molecular mass of 32 kDa using gel filtration and SDS-polyacrylamide gel electrophoresis. The enzyme showed higher specificity with ascorbate than with pyrogallol. The K(m) values of the enzyme for ascorbate and H2O2 were 111 +/- 8.9 and 20 +/- 2.5 microM, respectively. When the enzyme was diluted with the ascorbate-deleted medium, the half inactivation time was approximately 15 min. The absorption spectra of the purified enzyme and the inhibition by cyanide and azide showed that it is a hemoprotein. The enzyme was markedly inhibited by 0.2 mM p-chloromercuribenzoate. The enzyme cross-reacted by immunoblotting with the monoclonal antibody raised against Euglena cytosolic AsAP. The amino acid sequences in the N-terminal region of Chlorella AsAP showed no significant similarity to any other AsAPs from higher plants and algae.

Amino Acid Sequence↗
PubMed2002

Purification and characterization of a corrinoid compound from Chlorella tablets as an algal health food.

Vitamin B(12) content of an algal health food, Chlorella tablets (Chlorella sp.), was determined by both Lactobacillus leichmannii ATCC 7830 microbiological and intrinsic factor-chemiluminescence methods. The values of 200.9-211.6 microg/100 g dry weight determined by the chemiluminescence method were similar to the values (201.3-285.7 microg/100 g dry weight) determined by the microbiological method. A corrinoid compound was purified to homogeneity from the Chlorella tablets and characterized. The purified corrinoid compound was identified as vitamin B12, on the basis of silica gel 60 TLC, C18 reversed-phase HPLC, 1H NMR spectroscopy, and UV-Vis spectroscopy.

Chlorella↗
PubMed1998

Characterization of a novel cis-syn and trans-syn-II pyrimidine dimer glycosylase/AP lyase from a eukaryotic algal virus, Paramecium bursaria chlorella virus-1.

Endonuclease V from bacteriophage T4, is a cis-syn pyrimidine dimer-specific glycosylase. Recently, the first sequence homolog of T4 endonuclease V was identified from chlorella virus Paramecium bursaria chlorella virus-1 (PBCV-1). Here we present the biochemical characterization of the chlorella virus pyrimidine dimer glycosylase, cv-PDG. Interestingly, cv-PDG is specific not only for the cis-syn cyclobutane pyrimidine dimer, but also for the trans-syn-II isomer. This is the first trans-syn-II-specific glycosylase identified to date. Kinetic analysis demonstrates that DNAs containing both types of pyrimidine dimers are cleaved by the enzyme with similar catalytic efficiencies. Cleavage analysis and covalent trapping experiments demonstrate that the enzyme mechanism is consistent with the model proposed for glycosylase/AP lyase enzymes in which the glycosylase action is mediated via an imino intermediate between the C1' of the sugar and an amino group in the enzyme, followed by a beta-elimination reaction resulting in cleavage of the phosphodiester bond. cv-PDG exhibits processive cleavage kinetics which are diminished at salt concentrations greater than those determined for T4 endonuclease V, indicating a possibly stronger electrostatic attraction between enzyme and DNA. The identification of this new enzyme with broader pyrimidine dimer specificity raises the intriguing possibility that there may be other T4 endonuclease V-like enzymes with specificity toward other DNA photoproducts.

Binding Sites↗
PubMed1999

The catalytic mechanism of a pyrimidine dimer-specific glycosylase (pdg)/abasic lyase, Chlorella virus-pdg.

The repair of UV light-induced cyclobutane pyrimidine dimers can proceed via the base excision repair pathway, in which the initial step is catalyzed by DNA glycosylase/abasic (AP) lyases. The prototypical enzyme studied for this pathway is endonuclease V from the bacteriophage T4 (T4 bacteriophage pyrimidine dimer glycosylase (T4-pdg)). The first homologue for T4-pdg has been found in a strain of Chlorella virus (strain Paramecium bursaria Chlorella virus-1), which contains a gene that predicts an amino acid sequence homology of 41% with T4-pdg. Because both the structure and critical catalytic residues are known for T4-pdg, homology modeling of the Chlorella virus pyrimidine dimer glycosylase (cv-pdg) predicted that a conserved glutamic acid residue (Glu-23) would be important for catalysis at pyrimidine dimers and abasic sites. Site-directed mutations were constructed at Glu-23 to assess the necessity of a negatively charged residue at that position (Gln-23) and the importance of the length of the negatively charged side chain (Asp-23). E23Q lost glycosylase activity completely but retained low levels of AP lyase activity. In contrast, E23D retained near wild type glycosylase and AP lyase activities on cis-syn dimers but completely lost its activity on the trans-syn II dimer, which is very efficiently cleaved by the wild type cv-pdg. As has been shown for other glyscosylases, the wild type cv-pdg catalyzes the cleavage at dimers or AP sites via formation of an imino intermediate, as evidenced by the ability of the enzyme to be covalently trapped on substrate DNA when the reactions are carried out in the presence of a strong reducing agent; in contrast, E23D was very poorly trapped on cis-syn dimers but was readily trapped on DNA containing AP sites. It is proposed that Glu-23 protonates the sugar ring, so that the imino intermediate can be formed.

Bacteriophage T4↗
PubMed2004

Functional analysis of FAD-dependent thymidylate synthase ThyX from Paramecium bursaria Chlorella virus-1.

Sequence analysis of the 330-kb double-stranded DNA genome of Paramecium bursaria chlorella virus-1 revealed an open reading frame A674R that encodes a protein with up to 53% amino acid identity to a recently discovered new class of thymidylate synthases, called ThyX. Unlike the traditional thymidylate synthase, ThyA, that uses methylenetetrahydrofolate (CH(2)H(4)folate) as both a source of the methylene group and the reductant, CH(2)H(4)folate only supplies the methylene group in ThyX-catalyzed reactions. Furthermore, ThyX only catalyzes thymidylate (dTMP) formation in the presence of reduced pyridine nucleotides and oxidized FAD. The distribution and transcription patterns of the a674r gene in Chlorella viruses were examined. The a674r gene was cloned, and the protein was expressed in Escherichia coli. Biochemical characterization of the P. bursaria chlorella virus-1 recombinant ThyX protein indicates that it is more efficient at converting dUMP to dTMP than previously studied ThyX enzymes, thus allowing more detailed mechanistic studies of the enzyme. The ThyX-dUMP complexes with bound FAD function as efficient NAD(P)H oxidases, indicating that dUMP binds to the enzyme prior to NAD(P)H. This oxidation activity is directly linked to FAD reduction. Our results indicate that ThyX-specific inhibitors can be designed that do not affect ThyA enzymes. Finally, a model is proposed for the early stages of ThyX catalysis.

Animals↗
PubMed1997

Identification of Chlorella T-1 ingredient which enhances DMPO-OH adduct formation in Fenton reaction.

Chlorella T-1 is a micro algae which carries out highly active photosynthetic carbon fixation. For searching the OH scavenging molecules in this strain, the methanol extract of T-1 was fractionated by RP-HPLC and the fractions were analyzed for DMPO-OH formation by ESR after Fenton reaction. In the course of study, a single chlorella T-1 ingredient was found to enhance the formation of DMPO-OH rather than scavenge in the Fenton system. The OH enhancing chlorella component was further purified by chromatography and finally identified as lactic acid by NMR and LC-MS. From the analysis of the reaction conditions for DMPO-OH, it was found that lactic acid did not serve as direct source of OH but accelerated Fenton reaction.

Chlorella↗
PubMed2002

Kinetics of adsorption and uptake of Cu2+ by Chlorella vulgaris: influence of pH, temperature, culture age, and cations.

Adsorption and uptake of Cu2+ by Chlorella vulgaris were distinguished by extracting the surface-bound Cu2+ with EDTA. The uptake of Cu2+ followed Michaelis Menten kinetics. The maximum rate of Cu2+ uptake (0.362fmolcell(-1) h(-1)) was obtained at pH 6.0. The rate of Cu2+ uptake was greater for cultures in the exponential phase of growth, and increased with a rise in temperature from 6 to 25 degrees C, thus pointing towards an active mechanism. The maximum number of Cu2+ binding sites was 3.245 fmol cell(-1) at pH 4.5. Adsorption of Cu2+ was strongly pH-dependent thereby indicating that the number and nature of metal binding sites on the cell surface change with changing chemistry of the solution. Unlike uptake, the adsorption remained unaffected by small changes in temperature. Older cultures displayed a higher Cu2+ adsorption capacity than the exponentially growing ones thus suggesting generation of new and/or additional Cu2+ binding sites on older cells of C. vulgaris. By pH titration, the cation-exchange capacity of Chlorella, measured in terms of H+/ Na+ exchange, was about 17 fmol cell(-1) at pH 10.5. Negligible cation exchange capacity at and below pH 5.0 indicated that ion exchange was not the sole mechanism of Cu2+ adsorption by Chlorella. The uptake and adsorption of Cu2+ were inhibited by 100 microM of various cations including other heavy metal ions. The general concept that cations competitively inhibit accumulation of metals in living organisms does not hold for C. vulgaris. Non-competitive, uncompetitive and mixed inhibition of Cu2+ uptake and adsorption by various cations were more common than competitive inhibition.

Adsorption↗
PubMed2004

Effects of chlorella on activities of protein tyrosine phosphatases, matrix metalloproteinases, caspases, cytokine release, B and T cell proliferations, and phorbol ester receptor binding.

A Chlorella powder was screened using 52 in vitro assay systems for enzyme activity, receptor binding, cellular cytokine release, and B and T cell proliferation. The screening revealed a very potent inhibition of human protein tyrosine phosphatase (PTP) activity of CD45 and PTP1C with 50% inhibitory concentration (IC(50)) values of 0.678 and 1.56 microg/mL, respectively. It also showed a moderate inhibition of other PTPs, including PTP1B (IC(50) = 65.3 microg/mL) and T-cell-PTP (114 microg/mL). Other inhibitory activities and their IC(50) values included inhibition of the human matrix metalloproteinases (MMPs) MMP-1 (127 microg/mL), MMP-3 (185 microg/mL), MMP-7 (18.1 microg/mL), and MMP-9 (237 microg/mL) and the human peptidase caspases caspase 1 (300 microg/mL), caspase 3 (203 microg/mL), caspase 6 (301 microg/mL), caspase 7 (291 microg/mL), and caspase 8 (261 microg/mL), as well as release of the cytokines interleukin (IL)-1 (44.9 microg/mL), IL-2 (14.8 microg/mL), IL-4 (49.2 microg/mL), IL-6 (34.7 microg/mL), interferon-gamma (31.6 microg/mL), and tumor necrosis factor-alpha (11 microg/mL) from human peripheral blood mononuclear cells. Chlorella also inhibited B cell proliferation (16.6 microg/mL) in mouse splenocytes and T cell proliferation (54.2 microg/mL) in mouse thymocytes. The binding of a phorbol ester, phorbol 12,13-dibutyrate, to its receptors was also inhibited by Chlorella with an IC(50) of 152 microg/mL. These results reveal potential pharmacological activities that, if confirmed by in vivo studies, might be exploited for the prevention or treatment of several serious pathologies, including inflammatory disease and cancer.

Animals↗
PubMed1997

Zepp, a LINE-like retrotransposon accumulated in the Chlorella telomeric region.

Six copies of insertion elements accumulate in the subtelomeric region immediately proximal to the telomeric repeats on Chlorella chromosome I. The elements, designated Zepps, bear the characteristic features of non-viral (LINE-like) retrotransposons, including a poly(A) tail, 5'-truncations, a retroviral reverse transcriptase-like ORF and flanking target duplications. Detailed sequence analysis of the Chlorella subtelomeric region revealed a novel mechanism of Zepp transposition; successive insertions of each Zepp element into another Zepp as a target, leaving a tandem array of their 3'-regions with poly(A) tracts facing toward the centromere. Only the most distal Zepp copy was inverted to connect its poly(A) tail with the telomeric repeats. A similar Zepp cluster but without the telomeric repeats was also found at the terminus of another Chlorella chromosome. These structures contrast with that proposed for the addition of HeT-A and TART elements to Drosophila telomeres. Expression of Zepp elements is induced by heat shock treatment. Possible roles of the subtelomeric retrotransposons in formation and maintenance of telomeres are discussed.

Amino Acid Sequence↗
PubMed1991

Molecular cloning and characterization of the gene encoding the adenine methyltransferase M.CviRI from Chlorella virus XZ-6E.

The gene encoding the DNA methyltransferase M.CviRI from Chlorella virus XZ-6E was cloned and expressed in Escherichia coli. M.CviRI methylates adenine in TGCA sequences. DNA containing the M.CviRI gene was sequenced and a single open reading frame of 1137 bp was identified which could code for a polypeptide of 379 amino acids with a predicted molecular weight of 42,814. Comparison of the M.CviRI predicted amino acid sequence with another Chlorella virus and 14 bacterial adenine methyltransferases revealed extensive similarity to the other Chlorella virus enzyme.

Amino Acid Sequence↗
PubMed1975

Characterization and messenger activity of poly(A)-containing RNA from Chlorella.

Poly(A)-containing RNA was isolated by cellulose column chromatography from total RNA extracted from Chlorella fusca var. vacuolata 211/8p. RNA retained by the column was identified as poly(A)-containing RNA because it contained ribonuclease-resistant tracts, 25 to 55 nucleotides in length, from which not less than 80% of base was found to be adenine after acid hydrolysis. The base composition of poly(A)-containing RNA differed from that of RNA (largely ribosomal) which did not adsorb to cellulose, having a higher adenine content and a lower guanine content. Poly(A)-containing RNA was polydisperse including molecules with mobilities from 10S to 40S with a mean of about 20S. In an in vitro system derived from wheat-germ, protein synthesis was stimulated by adding poly(A)-containing RNA from Chlorella. Optimum conditions were established in this system with respect to the amount of poly(A)-containing RNA added and the concentration of KCl and Mg-2+. It is proposed that, in Chlorella, poly(A)-containing RNA includes cytoplasmic mRNA as has been shown for some other eucaryotic organisms.

Adenine Nucleotides↗
PubMed1997

Chlorella virus PBCV-1 encodes a homolog of the bacteriophage T4 UV damage repair gene denV.

The bacteriophage T4 denV gene encodes a well-characterized DNA repair enzyme involved in pyrimidine photodimer excision. We have discovered the first homologs of the denV gene in chlorella viruses, which are common in fresh water. This gene functions in vivo and also when cloned in Escherichia coli. Photodamaged virus DNA can also be photoreactivated by the host chlorella. Since the chlorella viruses are continually exposed to solar radiation in their native environments, two separate DNA repair systems, one that functions in the dark and one that functions in the light, significantly enhance their survival.

Amino Acid Sequence↗
PubMed1977

Specific deficit in the synthesis of 6-sulfoquinovsyl diglyceride in Chlorella pyrenoidosa.

It was found that when Chlorella pyrenoidosa was grown on cysteine as the sole sulfur source, it lost the ability to grow photoautotrophically. When grown in the presence of glucose, cysteine-grown cells displayed a doubling time in the light or dark of 45 h, which is identical to that of cells grown on glucose and SO4 in the dark. This suggests that cells grown on cysteine as sole sulfur source can only grow heterotrophically. In support of this hypothesis, it was found that cysteine-grown cells were defective both in vivo and in vitro in CO2 fixation, although O2 evolution in such cells was normal. Assays of the enzymes of the Calvin cycle indicated that the deficit in CO2 fixation could be ascribed to a lowered phosphoribulokinase activity. A total lipid analysis of Chlorella grown on cysteine revealed that such cells showed a 100-fold deficiency in the purportedly chloroplast-associated 6-sulfoquinovsyl diglyceride. This agrees with earlier reports that cysteine could not serve as a precursor of sulfolipid in Chlorella. No other polar lipid was affected. Large amounts of triglyceride, however, were found in cysteine-grown cells. The biosynthesis of triglyceride provides a means of utilizing reduced nicotinamide adenine dinucleotide reducing equivalents not being used for CO2 fixation.

Chlorella↗
PubMed1986

Restriction endonuclease activity induced by PBCV-1 virus infection of a Chlorella-like green alga.

An enzyme was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1 which exhibits type II restriction endonuclease activity. The enzyme recognized the sequence GATC and cleaved DNA 5' to the G. Methylation of deoxyadenosine in the GATC sequence inhibited enzyme activity. In vitro the enzyme cleaved host Chlorella nuclear DNA but not viral DNA because host DNA contains GATC and PBCV-1 DNA contains GmATC sequences. PBCV-1 DNA is probably methylated in vivo by the PBCV-1-induced methyltransferase described elsewhere (Y. Xia and J. L. Van Etten, Mol. Cell. Biol. 6:1440-1445). Restriction endonuclease activity was first detected 30 to 60 min after viral infection; the appearance of enzyme activity required de novo protein synthesis, and the enzyme is probably virus encoded. Appearance of enzyme activity coincided with the onset of host DNA degradation after PBCV-1 infection. We propose that the PBCV-1-induced restriction endonuclease participates in host DNA degradation and is part of a virus-induced restriction and modification system in PBCV-1-infected Chlorella cells.

Base Sequence↗
PubMed1975

Enhancement of adhesion of the marine Chlorella vulgaris to glass.

The adhesion of washed cells of a marine Chlorella vulgaris to solid surfaces was enhanced by non-diffusible material recovered from Chlorella exudate, marine bacterial cultures, natural seawater, and fouled marine surfaces. Materials isolated from certain bacterial cultures and from particulate materials filtered from seawater were three orders of magnitude more active than Chlorella exudate per unit weight. Active polymer materials from several sources were chromatographed on DEAE cellulose. The major fraction eluted with dilute base contained both protein and carbohydrate and enhanced adhesion more than the unchromatographed material.

Bacteria↗
PubMed1989

Variability of allergenicity in eight strains of the green algal genus Chlorella.

Biochemical and immunological properties of allergen extracts from eight strains within four species of the unicellular green alga Chlorella were compared. The total protein and carbohydrate contents ranged from 13 to 29 and 18 to 47% of the dry weight, respectively. It was shown, both with RAST inhibition and immunoblotting, that Chlorella contain components which specifically bind to patient IgE antibodies. The relative allergen potency as assayed by RAST inhibition varied fivefold. Between seven and twenty IgE-binding components were identified in the various strains with molecular weights from 13 to 80 kD. Thus, the use of thoroughly characterized Chlorella strains is mandatory for preparation of relevant allergen extracts.

Allergens↗
PubMed1988

A heterotrophic synchronous culture of Chlorella.

Based on the observation that photoautotrophically grown Chlorella cells fail to complete cell division under anaerobic condition in the dark, we devised a heterotrophic synchronous culture (HSC) system for this green alga. The system consists, at a temperature of 21 degrees C, of a 32 +/- 1 h period under 3% CO2 in air and the successive 12 +/- 1 h period under 0.5% O2 +/- 99.5% N2 (the sum of the two periods is equal to 44 +/- 1 h), using a semi-balanced medium containing glucose in an inorganic salt solution. This procedure could be successively repeated several times and the division index was practically 100%, as it is for Chlorella in the photoautotrophic synchronous culture (PSC). We believe this is the first successful HSC achieved by the method of alternating atmospheric oxygen tension. Synthetic patterns for DNA, RNA and protein as well as chlorophyll during the cell cycle of Chlorella in HSC were similar to those observed in PSC, and the respiratory activity of actively growing cells in HSC was twice that of those in PSC. It is hoped that this system, under the regimen of high and low oxygen tension, can be utilized for other eukaryotic cells.

Cell Count↗
PubMed2002

Two low-temperature-inducible Chlorella genes for delta12 and omega-3 fatty acid desaturase (FAD): isolation of delta12 and omega-3 fad cDNA clones, expression of delta12 fad in Saccharomyces cerevisiae, and expression of omega-3 fad in Nicotiana tabacum.

In an attempt to clarify the involvement of fatty acid desaturases (FADs) in the freezing tolerance of Chlorella vulgaris IAM C-27, developed by hardening, we have isolated cDNA clones for two types of FADs from the Chlorella strain, based on the sequence information of genes for delta12 and omega-3 FADs, respectively desaturating oleic acid (18:1) to linoleic acid (18:2) and linoleic acid (18:2) to linolenic acid (18:3). The deduced amino acid sequence of the first clone, designated CvFad2, showed about 66% similarity to the microsomal delta12 FADs from several higher plants and this gene had delta12 FAD activity when expressed in Saccharomyces cerevisiae. The predicted protein encoded by a second gene, designated CvFad3, showed about 60% similarity to the microsomal and plastidial omega-3 FADs from several higher plants. The features of the amino acid sequences of the C- and N-terminal regions of CvFAD3 and fatty acid analysis of polar lipids in transgenic tobacco plant expressing the CvFad3 gene suggested that this gene encodes the microsomal omega-3 FAD. Southern blot analysis showed that both genes were single-copy genes in the genome of the Chlorella strain. Different transcriptional patterns were observed with the two genes during hardening in Northern blot analysis.

Amino Acid Sequence↗