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PubMed2006

Structural studies on peanut lectin complexed with disaccharides involving different linkages: further insights into the structure and interactions of the lectin.

Crystal structures of peanut lectin complexed with Galbeta1-3Gal, methyl-T-antigen, Galbeta1-6GalNAc, Galalpha1-3Gal and Galalpha1-6Glc and that of a crystal grown in the presence of Galalpha1-3Galbeta1-4Gal have been determined using data collected at 100 K. The use of water bridges as a strategy for generating carbohydrate specificity was previously deduced from the complexes of the lectin with lactose (Galbeta1-4Glc) and T-antigen (Galbeta1-3GalNAc). This has been confirmed by the analysis of the complexes with Galbeta1-3Gal and methyl-T-antigen (Galbeta1-3GalNAc-alpha-OMe). A detailed analysis of lectin-sugar interactions in the complexes shows that they are more extensive when the beta-anomer is involved in the linkage. As expected, the second sugar residue is ill-defined when the linkage is 1-->6. There are more than two dozen water molecules which occur in the hydration shells of all structures determined at resolutions better than 2.5 A. Most of them are involved in stabilizing the structure, particularly loops. Water molecules involved in lectin-sugar interactions are also substantially conserved. The lectin molecule is fairly rigid and does not appear to be affected by changes in temperature.

Disaccharides↗
PubMed1976

Methylation analysis of glucosaminitol and glucosaminyl-glucosaminitol disaccharides. Formation of 2-deoxy-2-(N-acetylacetamido)-glucitol derivatives.

N-Acetylglucosaminitol, N-acetylglucosaminyl-beta 1',4-N-acetylglucosaminitol (chitobiitol), the corresponding trimer (chitotriitol) and N-acetylgucosaminyl-beta 1'6-N-acetylglucosaminitol were subjected to methylation analysis using combined gas-liquid chromatography/mass spectrometry. The preparation were subjected to permethylation according to Hakomori, followed by acid hydrolysis, reduction and peracetylation. From N-acetylglucosaminitol and its 4-0 and 6-0 substituted derivatives, methylated N-acetylacetamido derivatives were obtained. The possible conditions for the formation of these products are discussed.

Acetylglucosamine↗
PubMed1985

Glycosphingolipids in insects. Chemical structures of ceramide monosaccharide, disaccharide, and trisaccharide from pupae of Calliphora vicina (Insecta: Diptera).

The presence of glycosphingolipids in the pupae of the blowfly, Calliphora vicina, was established. The thin layer chromatographic pattern of the total neutral glycolipids revealed the presence of more than 13 components, the major one being ceramide monohexoside. By the use of high performance liquid chromatography, the three simplest components were isolated and their chemical structures determined: Glc(beta 1-1)Cer, Man(beta 1-4)-Glc(beta 1-1)Cer [with minor component Gal(beta 1-4)Glc(beta 1-1)Cer] and GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)-Cer. The ceramide composition of the parent insect glycosphingolipids is dominated by the 20:0 fatty acid, arachidic acid, and the sphingoid tetradecasphing-4-enine.

Animals↗
PubMed1985

Biosynthesis of wall teichoic acids in Staphylococcus aureus H, Micrococcus varians and Bacillus subtilis W23. Involvement of lipid intermediates containing the disaccharide N-acetylmannosaminyl N-acetylglucosamine.

The precursors for linkage unit (LU) synthesis in Staphylococcus aureus H were UDP-GlcNAc, UDP-N-acetylmannosamine (ManNAc) and CDP-glycerol and synthesis was stimulated by ATP. Moraprenol-PP-GlcNAc-ManNAc-(glycerol phosphate)1-3 was formed from chemically synthesised moraprenol-PP-GlcNAc, UDP-ManNAc and CDP-glycerol in the presence of Triton X-100. LU intermediates formed under both conditions served as acceptors for ribitol phosphate residues, from CDP-ribitol, which comprise the main chain. The initial transfer of GlcNAc-1-phosphate from UDP-GlcNAc was very sensitive to tunicamycin whereas the subsequent transfer of ManNAc from UDP-ManNAc was not. Poly(GlcNAc-1-phosphate) and LU synthesis in Micrococcus varians, with endogenous lipid acceptor, UDP-GlcNAc and CDP-glycerol, was stimulated by UDP-ManNAc. Synthesis of LU on exogenous moraprenol-PP-GlcNAc, with Triton X-100, was dependent on UDP-ManNAc and CDP-glycerol and the intermediates formed served as substrates for polymer synthesis. Membranes from Bacillus subtilis W23 had much lower levels of LU synthesis, but UDP-ManNAc was again required for optimal synthesis in the presence of UDP-GlcNAc and CDP-glycerol. Conditions for LU synthesis on exogenous moraprenol-PP-GlcNAc were not found in this organism. LU synthesis on endogenous acceptor in the absence of UDP-ManNAc was explained by contamination of membranes with UDP-GlcNAc 2-epimerase. Under appropriate conditions, low levels of this enzyme were sufficient to convert UDP-GlcNAc into a mixture of UDP-Glc-NAc and UDP-ManNAc and account for LU synthesis. The results indicate the formation of prenol-PP-GlcNAc-ManNAc-(glycerol phosphate)1-3 which is involved in the synthesis of wall teichoic acids in S. aureus H, M. varians and B. subtilis W23 and their attachment to peptidoglycan.

Bacillus subtilis↗
PubMed1994

Lipid modulation of glycolipid receptor function. Availability of Gal(alpha 1-4)Gal disaccharide for verotoxin binding in natural and synthetic glycolipids.

Verotoxins bind to glycosphingolipids containing terminal Gal(alpha 1-4)Gal residues. Globotriaosylceramide is the most effective receptor for verotoxin-1 in vitro and is the functional plasma-membrane receptor which mediates cytopathology for most sensitive cells. Binding of verotoxin-1 to a series of galabiose-containing or globotriaose-containing synthetic glycolipids with monoalkylsulfides and bisalkylsulfides or sulfones as the lipid moiety, have been studied for toxin binding by TLC overlay and in solid phase in the presence of auxiliary lipids. The results demonstrate that for an identical carbohydrate, binding is dramatically altered according to the nature of the lipid moiety. The close proximity of the galabiose sequence and the hydrophobic species also compromised recognition. The lipid environment is also a major determinant of receptor function, since species that were effective, even preferred toxin receptors as monitored by TLC overlay, were not necessarily recognized in the presence of auxiliary lipids. Certain glycolipids, which were not recognized by TLC overlay, were nevertheless found to be effective receptors in an auxiliary lipid matrix. These results demonstrate the crucial role of the lipid moiety in verotoxin/glycolipid recognition and are discussed in relation to toxin pathogenesis and glycolipid receptor function.

Bacterial Toxins↗
PubMed1978

Identification of Salmonella bacteria by co-agglutination, using antibodies against synthetic disaccharide-protein antigens O2, O4 and O9, adsorbed to protein A-containing staphylococci.

Protein A-containing staphylococci sensitized with antisera against synthetic Salmonella O-antigens 2, 4 and 9, representative of serogroups A, B and D, respectively, were used for identification of Salmonella bacteria by co-agglutination. Out of 416 Salmonella bacteria tested the reagents correctly identified all 24 serogroup A strains, 119 serogroup B strains and 39 serogroup D strains. Unexpected agglutination was registered with two of 144 strains belonging to serogroup C 2 with reagent containing antiserum against synthetic O antigen 4. No agglutination occurred when 24 non-Salmonella bacterial strains were tested. Approximately 10(8)bacteria were required for positive co-agglutination. As compared to standard slide agglutination with conventional anti-Salmonella O factor sera, the co-agglutination metod was favourable in that the reactions were stronger, although the concentration of antiserum used was from 20 to 200 times lower. The co-agglutination method could also be used for detection of soluble antigens in the form of lipopolysaccharides from Salmonella bacteria in concentrations of 1 microgram/ml. When the sensitivity of the co-agglutination technique was compared with indirect immunofluorescence (IFL), the IFL method was shown to be at least 1000 times more sensitive.

Adsorption↗
PubMed1973

Carbohydrate metabolism in lactic streptococci: fate of galactose supplied in free or disaccharide form.

Phosphorylation of free galactose by lactic streptococci was mediated by an adenosine triphosphate (ATP)-dependent kinase. The phosphoenolpyruvate (PEP) phosphotransferase system (PTS) was involved to a limited extent in transport of the sugar. The conversion of free galactose to glucose also was demonstrated, and uridine diphosphogalactose-4-epimerase was demonstrated to account for this change. Galactose, supplied as lactose, was phosphorylated during transport by means of the PTS with PEP as the phosphate donor. Data also indicated that galactose derived from lactose was catabolized by the glycolytic pathway. Results showed the participation of ATP or PEP, or both, in the phosphorylation of five growth sugars for lactic streptococci, namely, galactose, glucose, lactose, maltose, and mannose. Free galactose was phosphorylated exclusively by ATP except when cells were grown on galactose; in this case, slight involvement of PEP in phosphorylation also was noted. Lactose phosphorylation was much more effective with PEP except when cells were grown on lactose, in which case ATP was equally effective. Glucose was phosphorylated to about the same degree by either ATP or PEP.

Adenosine Triphosphate↗
PubMed1983

Non-cariogenicity of the disaccharide palatinose in experimental dental caries of rats.

The caries-inducing activity of palatinose (isomaltulose, alpha-D-glucopyranosyl-1,6-fructose) was examined in in vitro and in vivo experiments, comparing it with other carbohydrates. When Streptococcus mutans was successively subcultured in a broth medium containing 1% palatinose, the strains belonging to serotype a, d, or g did not ferment palatinose, whereas the strains belonging to serotype b, c, e, or f did ferment palatinose. Furthermore, palatinose significantly inhibited the synthesis of insoluble glucan from sucrose by S. mutans. Specific-pathogen-free rats which had been infected with S. mutans 6715 and fed a diet containing 56% palatinose did not develop significant dental caries. However, rats infected similarly, but fed a diet containing sucrose, glucose, fructose, or a glucose-fructose mixture manifested significant caries when compared with the noninfected, sucrose-fed control rats. Furthermore, it was found that replacement of half of the sucrose content with palatinose resulted in decreased caries development compared with caries development in rats fed the sucrose diet.

Animals↗