Structure and anticancer activity of a new lectin from the cultivated red alga, Kappaphycus striatus.

The red alga Kappaphycus striatus is economically important food species and extensively cultivated throughout most tropical parts of the world as a source of carrageenan. In this note, the primary structure of a new lectin KSL from this alga was elucidated by the rapid amplification method of complementary DNA (cDNA) ends, which consists of 267 amino acid residues distributed in four tandem-repeated domains of about 67 amino acids and sharing 43% of identity. The calculated molecular mass from the deduced sequence was consistent with that of natural KSL (27,826 Da) determined by electron spray ionization-mass spectrometry. The primary structure of KSL showed high similarity to those of the high mannose N-glycan specific lectins from marine red algae, ESA-2 from Eucheuma serra, EDA-2 from Eucheuma denticulatum, KSA-2 from Kappaphycus striatum, KAAs from Kappaphycus alvarezii and SfLs from Solieria filiformis, and from microorganisms, BOA from Burkholderia oklahomensis, MBHA from Myxococcus xanthus, OAA from Oscillatoria agardhii and PFL from Pseudomonas fluorescens. Furthermore, KSL showed anticancer effects against five carcinoma cell lines, HT29, Hela, MCF-7, SK-LU-1 and AGS, in a dose-dependent manner with the IC50 values of 0.80-1.94 µM, whereas its inhibition activities on cancer cells were not detected in the presence of yeast mannan, an inhibitor against lectin KSL. The cultivated red alga K. striatus could also be a good source of functional lectin(s) for application as anticancer agents.

Assessment of radioactivity and chemical contaminants in domestic water at supply stations in Long Phu District, Vietnam, to prevent public health risks.

This paper presents information on the concentration of radioactivity and chemicals at 12 water stations that used groundwater as their raw water supply source. The groundwater's radioactivity was higher than the treated, tap, and surface water, but lower than the national and international recommendations. At five stations (41.7%), the gross alpha contents were higher than the levels advised by Vietnam's regulations, but met the WHO and IAEA's recommendations. The mean activity (Bq L-1) gross alpha, gross beta, Ra-224, Ra-226, and Ra-228 were 0.093 ± 0.012, 0.221 ± 0.020, 0.031 ± 0.004, 0.028 ± 0.004, and 0.035 ± 0.001, respectively. The contribution of Ra-226 to the gross alpha was in a range of 23%-60% (r = 0.91, p value <0.001), and the ratio of Ra-226/Ra-228 ranged from 0.49-1.06. For the treated and tap water, each age groups' annual committed effective dose was lower than the international regulations. The concentration of the total dissolved solids, sulfate, chloride, sodium, barium, and manganese met the national regulations. However, during the rainy season, the surface water in the area was affected by saltwater intrusion, with salinity up to 4.1‰. Discriminant analysis was applied to study the differences among the water groups. As a result, the treated and tap water were separated from the others.

Simultaneous Determination of Gross Alpha/Beta Activities in Groundwater for Ingestion Effective Dose and its Associated Public Health Risk Prevention.

This paper presents information on the gross alpha and gross beta activity concentrations of two hundred twenty-six groundwater samples collected by gas flow proportional counters in southern Vietnam. The gross alpha results in the water samples ranged from 0.024 to 0.748 Bq L-1 with a mean of 0.183 ± 0.034 Bq L-1, and the gross beta results in the water samples ranged from 0.027-0.632 Bq L-1 with a mean of 0.152 ± 0.015 Bq L-1. The values obtained in this work were compared with those previously published for various regions or countries. Next, untreated and treated groundwater samples were analyzed to assess their influences on the treatment process. The results showed that there were differences in the minimum detection concentrations and the mean activity values between the untreated and treated groundwater samples (The p-value of the mean comparison tests is significant with p < 0.05). In both sample groups, there was a strong positive correlation of the gross alpha versus the gross beta results (r > 0.6). This means that among the radionuclides, the major sources of beta radiation are uranium and thorium decay series radionuclides. Finally, the annual effective dose for adults (>17 years) was calculated based on the assumption that major radionuclides have the highest effective dose conversion factors. In general, the results for Pb-210, Ra-226, and Ra-228 were observed to be lower than the recommended reference values established by the World Health Organization and the International Atomic Energy Agency, except for the value of Po-210.

Purification, characterization and biological effect of lectin from the marine sponge Stylissa flexibilis (Lévi, 1961).

SFL, a lectin from the marine sponge Stylissa flexibilis was purified by cold ethanol precipitation followed by ion exchange chromatography on DEAE Sepharose column and Sephacryl S-200 gel filtration. SFL is a dimeric glycoprotein of 32kDa subunits linked by a disulfide bridge with a molecular mass of 64kDa by SDS-PAGE and 65kDa by Sephacryl S-200 gel filtration. SFL preferentially agglutinated enzyme treated human A erythrocytes. The activity of lectin was strongly inhibited by monosaccharide d-galactose and glycoproteins asialo-porcine stomach mucin and asialo-fetuin. The lectin was Ca2+ dependent, stable over a range of pH from 5 to 8, and up to 60°C for 30min. The N-terminal amino acid sequence of SFL was also determined and a blast search on amino acid sequences revealed that the protein showed similarity only with lectins from the marine sponge Spheciospongia vesparia. SFL caused agglutination of Vibrio alginolyticus and V. parahaemolyticus in a dose dependent manner and inhibited the growth rates of the virulent bacterial strains. Growth inhibition of V. alginolyticus and V. parahaemolyticus with SFL was not observed in the presence of d-galactose or asialo-porcine stomach mucin, suggesting that the lectin caused the agglutination through binding to the target receptor(s) on the surface of Vibrios. Thus, the marine sponge S. flexibilis could promise to be a good source of a lectin(s) that may be useful as a carbohydrate probe and an antibacterial reagent.

Purification, primary structure, and biological activity of the high-mannose N-glycan-specific lectin from cultivated Eucheuma denticulatum.

Three isolectins from cultivated Eucheuma denticulatum were isolated. They were commonly monomeric proteins of about 28 kDa with a range of averaged molecular weights from 27,834 to 27,868 Da among the isolectins and shared almost the same 20 N-terminal amino acid sequences. Complementary DNA (cDNA) cloning based on the rapid amplification cDNA ends (RACE) methods elucidated the full-length sequence of EDA-2 which encodes 269 amino acids, including initiating methionine, with four tandemly repeated domains of about 67 amino acids. The primary structure of EDA-2 is highly similar to those of the high-mannose N-glycan specific lectins including Oscillatoria agardhii (OAA) and Burkholderia oklahomensis EO147 (BOA) from cyanobacteria, Myxococcus xanthus (MBHA) and Pseudomonas fluorescens Pf0-1 (PFL) from bacteria, and ESA-2 from a macro red alga. The hemagglutination activities were commonly inhibited by the glycoproteins bearing high-mannose N-glycans, but not by monosaccharides examined, including mannose. In a direct binding experiment with pyridylaminated oligosaccharides, an isolectin EDA-2 exclusively bound to high-mannose type N-glycans, but not to other glycans that include complex types and a core pentasaccharide of N-glycans, indicating that it recognized the branched oligomannoside moiety. Its binding activity was subtly different among the oligomannoside structures examined, showing that the lectin has preference affinity for high-mannose type N-glycans with an exposed (α1-3) mannose residue in the D2 arm. Interestingly, EDAs, the mixture of three isolectins inhibited the growth of shrimp pathogenic bacterium, Vibrio alginolyticus, although it did not affect the growth of V. parahaemolyticus and V. harveyi. Growth inhibition of V. alginolyticus with EDAs was not observed in the presence of yeast mannan bearing high-mannose N-glycans, suggesting that EDAs caused the activity through binding to the target receptor(s) on the surface of V. alginolyticus. These results indicate that cultivated carrageenophyte E. denticulatum is a good source of a lectin(s) that may be useful as a carbohydrate probe and an antibacterial reagent.

High-mannose N-glycan-specific lectin from the red alga Kappaphycus striatum (Carrageenophyte).

From a fresh sample (1 kg) of cultivated red alga Kappaphycus striatum, three isolectins, KSA-1 (15.1 mg), KSA-2 (58.0 mg) and KSA-3 (6.9 mg), were isolated by a combination of extraction with aqueous ethanol, ethanol precipitation, and ion exchange chromatography. Isolated KSAs were monomeric proteins of about 28kDa having identical 20N-terminal amino acid sequences to each other. Their hemagglutination activities were not inhibited by monosaccharides, but inhibited by glycoproteins bearing high-mannose N-glycans. In a binding experiment with pyridylaminated oligosaccharides by centrifugal ultrafiltration-HPLC assay, the isolectin KSA-2 was exclusively bound to high-mannose type N-glycans, but not to other glycans. Including complex types and a pentasaccharide core of N-glycans, indicating that it recognized branched oligomannosides. The binding activity of KSA-2 was slightly different among high-mannose N-glycans examined, indicating that the lectin has a higher affinity for those having the exposed (α1-3) Man in the D2 arm. On the other hand, KSA-2 did not bind to a free oligomannose that is a constituent of the branched oligomannosides, implying that the portion of the core GlcNAc residue(s) of the N-glycans is also essential for binding. Thus, KSA-2 appears to recognize the extended carbohydrate structure with a minimal length of a tetrasaccharide, Man(α1-3)Man(α1-6)Man(ß1-4)GlcNAc. This study indicates that K. striatum, which has extensively been cultivated as a source of carrageenan, is a good source of a valuable lectin(s) that is strictly specific for high-mannose N-glycans.