Effect of Bifidobacterium bifidum DSM 20082 cytoplasmic fraction on human immune cells.

The objective of the present study was to determine the effect of the soluble cytoplasmic fraction from Bifidobacterium bifidum DSM 20082 (Bb) lysate on peripheral blood T cells. In peripheral blood mononuclear cells of healthy subjects, cytotoxic activity, proliferation, apoptosis, and up-regulation of CD8 or CD4 molecules in T cells were examined. When peripheral blood mononuclear cells were stimulated with Bb lysate, the main effect was observed in CD8+ cells as a significant increase of CD8 molecules in a dose-dependent manner, and this behavior was observed at 24, 48, and 72 h after stimulation; in contrast, stimulation with Bb lysate showed no effect on the up-regulation of CD4 molecules in T helper cells. Further Bb lysate did not induce proliferation activity in either CD8+ or CD4+ cells. Bb lysate induced activation of CD8+ cytotoxic activity against autologous monocytes. Around 80% of the cells stimulated with Bb lysate were positive to peanut agglutinin (PNA), suggesting that the stimulated CD8+ cells corresponded to activated/effector cellular populations. When apoptosis was determined, there were no differences between stimulated and non-stimulated cells. Our results indicate that Bb lysate is able to increase cytotoxic activity of peripheral CD8+ cells, without affecting lymphocyte survival.

Lectin from Phaseolus acutifolius var. escumite: chemical characterization, sugar specificity, and effect on human T-lymphocytes.

Purification of the lectin from Phaseolus acutifolius var. escumite was achieved by affinity chromatography on a column containing glutaraldehyzed membranes from blood group O erythrocytes. The lectin is a tetrameric glycoprotein of 121 kDa with 10% of sugar by weight composed by four subunits of 30 kDa as determined by SDS-PAGE. The lectin is composed of four isolectins as determined by ion-exchange chromatography on a mono-S column. The lectin and its isolectins showed identical NH2 terminal residues (ANDLSFNFQR FNETN) with homology to the PHA leucoagglutinin-precursor. Peptide mass fingerprint from each lectin isoform determined from tryptic peptides by MALDI-TOF (matrix assisted laser desorption ionization-time-of-flight) showed differences among subunits, thus suggesting microheterogeneity in their amino acid sequences or different glycosylation patterns. The lectin and its four isolectins agglutinated erythrocytes without serological specificity and showed mitogenic activity on human leukocytes; moreover, the main effect was rather toward CD8+ than to CD4+ human peripheral lymphocytes. The lectin from escumite was not inhibitable by simple sugars; however, the specificity of the lectin and its isoforms was mainly addressed toward galactose residues present in bi- or triantennary N-acetyllactosamine-type glycans.

Isolation of the receptor for the Amaranthus leucocarpus lectin from human T lymphocytes.

Amaranthus leucocarpus lectin (ALL) is specific for GalNAc, and recognizes human T cells. The receptor for ALL was purified from T cells using biotin-labeled lectin and avidin-agarose as affinity matrix. It is a 70-kDa glycoprotein, constituted mainly by serine, glycine, and glutamic acid; its glycosidic portion contains mainly GalNAc; galactose, sialic acid, mannose, and GlcNAc were identified at a lower proportion. By ionic strength chromatography, as well as double dimension electrophoresis, we identified four isoforms of the ALL-receptor. N-terminal amino acid was blocked both in the ALL-receptor and its isoforms, therefore, tryptic peptides of ALL-receptor, analyzed through MALDI-TOF, were compared with the relative values obtained from the NCBInr (ProFound 2004/06/01) database. Our results indicated that the tryptic peptides obtained showed 54% homology with a DnaK-core molecular chaperone, 47% with human KIAA protein, and 44% with heat shock protein 8. The most frequent phenotype of the CD4 or CD8 ALL+ T cells was CD45RA+ CD27+; 26% of ALL+ T cells were CD25+ and 13% were CD69+, indicating that the glycoprotein recognized by ALL is present mainly on naive or quiescent T cells.

Amino acid decarboxylase activity and other chemical characteristics as related to freshness loss in iced cod (Gadus morhua).

Biogenic amine levels and other biochemical indicators were measured to study the safety of and the loss of freshness in iced Atlantic cod. Biogenic amine content exhibited high variability during iced storage of Atlantic cod. Ornithine and lysine decarboxylase activity apparently increased at the end of the storage period. Amino acid activity was probably generated by endogenous amino acid decarboxylases of raw fish. No statistical differences were observed in the total volatile base fraction or in the ammonia or monomethylamine contents during iced storage. However, trimethylamine contents showed a significant exponential relationship with time and sensory score. Cod formed inosine as the major metabolite of IMP. The H and G indices showed a linear relationship with time and sensory score and served as good indicators of cod freshness quality. However, the K, Ki, and P indices showed a logarithmic relationship with time and sensory score. IMP, K, Ki, and P served as indicators of freshness lost during the early stages of chilled storage of cod.

Characterisation of glutamine fructose-6-phosphate amidotransferase (EC 2.6.1.16) and N-acetylglucosamine metabolism in Bifidobacterium.

Bifidobacterium bifidum, in contrast to other bifidobacterial species, is auxotrophic for N-acetylglucosamine. Growth experiments revealed assimilation of radiolabelled N-acetylglucosamine in bacterial cell walls and in acetate, an end-product of central metabolism via the bifidobacterial D: -fructose-6-phosphate shunt. While supplementation with fructose led to reduced N-acetylglucosamine assimilation via the D: -fructose-6-phosphate shunt, no significant difference was observed in levels of radiolabelled N-acetylglucosamine incorporated into cell walls. Considering the central role played by glutamine fructose-6-phosphate transaminase (GlmS) in linking the biosynthetic pathway for N-acetylglucosamine to hexose metabolism, the GlmS of Bifidobacterium was characterized. The genes encoding the putative GlmS of B. longum DSM20219 and B. bifidum DSM20082 were cloned and sequenced. Bioinformatic analyses of the predicted proteins revealed 43% amino acid identity with the Escherichia coli GlmS, with conservation of key amino acids in the catalytic domain. The B. longum GlmS was over-produced as a histidine-tagged fusion protein. The purified C-terminal His-tagged GlmS possessed glutamine fructose-6-phosphate amidotransferase activity as demonstrated by synthesis of glucosamine-6-phosphate from fructose-6-phosphate and glutamine. It also possesses an independent glutaminase activity, converting glutamine to glutamate in the absence of fructose-6-phosphate. This is of interest considering the apparently reduced coding potential in bifidobacteria for enzymes associated with glutamine metabolism.

The effect of sugars and free amino acids from the freshwater prawn Macrobrachium rosenbergii hemolymph on lectin activity and on oxidative burst.

We determined the effect of low molecular weight components (LMWC) from healthy juvenile and adult Macrobrachium rosenbergii hemolymph on lectin activity and oxidative burst (OB) in hemocytes. In an attempt to identify the LMWC that affect the lectin's hemagglutinating activity or oxidative burst, we determined the hemolymph carbohydrates and free amino acids (FAA) concentration. The LMWC (<2000 Da) were obtained after dialysis of the hemolymph. Our results showed that LMWC from juveniles exerted a greater inhibition on lectin than LMWC from adult hemolymph. Production of superoxide radicals by hemocytes was lower in the presence of juvenile (p<0.05) as compared to adult LMWC. FAA composition of the hemolymph and of LMWC from adults showed higher proportion of alanine (which corresponded to 25% of total FAA) and proline (>20%); whereas, in juveniles, the main FAA identified were glycine (>40%) and alanine (26%). N-Acetyl-D-glucosamine (GlcNAc) was the main sugar residue in the hemolymph and LMWC from juveniles; its concentration was 2.4 times higher than glucose (Glc), whereas, in adults, Glc was the main free sugar residue. Our results suggest that the proportion of FAA and carbohydrates in the hemolymph of M. rosenbergii seems to be correlated with the maturation process; furthermore, the high proportion of free GlcNAc and glycine regulate, in the juvenile stage, lectin activity and cellular oxidative mechanisms, respectively.

Isolation and characterization of the potential receptor for wheat germ agglutinin from human neutrophils.

Neutrophils participate in host protection and central to this process is the regulation of oxidative mechanisms. We purified by affinity chromatography the receptor for the GlcNAc-specific WGA from CD14+ CD16+ cell lysates (WGAr). The receptor is a 141 kDa glycoprotein constituted by two subunits of 78 and 63 kDa. It is mainly composed of Ser, Asx, and Gly, and, in a minor proportion, His, Cys, and Pro. Its glycan portion contains GlcNAc, Gal, and Man; NeuAc and GalNAc were identified in a minor proportion. The amino acid sequence of the WGA receptor was predicted from tryptic peptides by MALDI-TOF, both subunits showed homology with cytokeratin type II (26 and 29% for the 78 and 63 kDa subunits, respectively); the 78 kDa subunit showed also homology with the human transferrin receptor (24%). Antibodies against WGAr induce higher oxidative burst than WGA, determined by NBT reduction; however, this effect was inhibited (p < 0.05) with GlcNAc suggesting that WGAr participates as mediator in signal transduction in neutrophils.

Bifidobacterium longum requires a fructokinase (Frk; ATP:D-fructose 6-phosphotransferase, EC 2.7.1.4) for fructose catabolism.

Although the ability of Bifidobacterium spp. to grow on fructose as a unique carbon source has been demonstrated, the enzyme(s) needed to incorporate fructose into a catabolic pathway has hitherto not been defined. This work demonstrates that intracellular fructose is metabolized via the fructose-6-P phosphoketolase pathway and suggests that a fructokinase (Frk; EC 2.7.1.4) is the enzyme that is necessary and sufficient for the assimilation of fructose into this catabolic route in Bifidobacterium longum. The B. longum A10C fructokinase-encoding gene (frk) was expressed in Escherichia coli from a pET28 vector with an attached N-terminal histidine tag. The expressed enzyme was purified by affinity chromatography on a Co(2+)-based column, and the pH and temperature optima were determined. A biochemical analysis revealed that Frk displays the same affinity for fructose and ATP (Km(fructose) = 0.739 +/- 0.18 mM and Km(ATP) = 0.756 +/- 0.08 mM), is highly specific for D-fructose, and is inhibited by an excess of ATP (>12 mM). It was also found that frk is inducible by fructose and is subject to glucose-mediated repression. Consequently, this work presents the first characterization at the molecular and biochemical level of a fructokinase from a gram-positive bacterium that is highly specific for D-fructose.