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PubMedDate not supplied

The enzymatic synthesis of lipid A: molecular structure and biologic function of monosaccharide precursors.

Certain Escherichia coli mutants, deficient in phosphatidylglycerol, accumulate novel, glucosamine-derived phospholipids that appear to be very early precursors of lipid A. The simplest of these, lipid X, is a derivative of glucosamine-1-phosphate substituted with beta-hydroxymyristoyl moieties at positions 2 and 3. The discovery of lipid X makes it possible to predict a biosynthetic pathway and a unified structure for lipid A. In addition, the minimal molecular requirements for the mitogenic and endotoxic properties of lipopolysaccharides can be elucidated with compounds of this kind.

Animals↗
PubMed1992

Tritiated borohydride reduction of carbohydrates: reduction of individual monosaccharides, alone or in groups, results in highly divergent specific activities.

Reduction of carbohydrates by tritiated borohydride resulted in the production of alditols or glycosides with characteristically divergent specific radioactivities. Simultaneous reduction of individual sugars in the presence of a reference standard, talose, permitted the assignment of a unique specific radioactivity with respect to talitol as 100%. A variety of structures was examined, including neutral hexoses, free and acetylated aminosugars, ketohexoses and glycosides containing a fixed pyranose ring adjacent to a carbonyl group. In the latter case, the resulting steric hindrance severely restricted the incorporation of tritium. In both of the ketohexoses tested, the minor product of the two epimeric alditols exhibited the higher specific radioactivity. In all cases, reduction produced a characteristic and reproducible specific activity in which the values varied from 51 to 182% of that found for talose. These results are interpreted on the basis of generalizations concerning mechanism and predictive value.

Borohydrides↗
PubMed1993

Analysis of bacterial phospholipid markers and plant monosaccharides during forage degradation by Ruminococcus flavefaciens and Fibrobacter succinogenes in co-culture.

Marker components of the phospholipids of Ruminococcus flavefaciens and Fibrobacter succinogenes were identified for studies on the degradation of forage by these bacteria growing in mixed culture. The principal fatty acid methyl esters and dimethyl acetals detected varied between strains and were influenced by the addition of a mixture of higher volatile fatty acids and vitamins to the medium, but these effects were small compared to the differences between the species. When two strains of R. flavefaciens were grown on a mixture of clover and ryegrass, and on barley straw in the presence or absence of two strains of F. succinogenes, the solubilization of plant material tended to be lowered by the presence of F. succinogenes. R. flavefaciens was the predominant bacterium among colonies recovered from roll tubes, and the phospholipids were primarily those of R. flavefaciens. Analysis of the culture supernatant liquids showed that F. succinogenes produced greater amounts of free and bound xylose from both clover and straw than did R. flavefaciens. With both forages, cultures containing the two species produced more soluble free arabinose, and less soluble-bound arabinose, than either species grown alone.

Animal Feed↗
PubMed1994

Interactions between rumen bacterial strains during the degradation and utilization of the monosaccharides of barley straw cell-walls.

Pure cultures and pair-combinations of strains representative of the rumen cellulolytic species Ruminococcus flavefaciens, Fibrobacter succinogenes and Butyrivibrio fibrisolvens were grown on cell-wall materials from barley straw. Of the pure cultures, R. flavefaciens solubilized straw most rapidly. The presence of B. fibrisolvens, which was unable to degrade straw extensively in pure culture, increased the solubilization of dry matter by R. flavefaciens and the solubilization of cell-wall carbohydrates by both R. flavefaciens and F. succinogenes. During fermentation, both R. flavefaciens and F. succinogenes released bound glucose and free and bound arabinose and xylose into solution. The accumulation of these sugars, especially arabinose and xylose, was greatly reduced in co-cultures containing B. fibrisolvens, suggesting that significant interspecies cross feeding of the products of hemicellulose hydrolysis (particularly soluble bound xylose released by F. succinogenes) occurs during straw degradation by mixed cultures containing this species.

Animal Feed↗
PubMed1990

Synthesis of O-glycosylated tuftsins by utilizing threonine derivatives containing an unprotected monosaccharide moiety.

Synthesis is described of four tuftsin derivatives containing a D-glucopyranosyl or a D-galactopyranosyl unit covalently linked to the hydroxy side chain function of the threonine residue through either an alpha or beta O-glycosidic linkage. Fmoc-threonine derivatives containing the suitable unprotected sugar were used for incorporating the O-glycosylated amino acid residue. Z-Thr[alpha-Glc(OBzl)4]-OBzl and Z-Thr[alpha-Gal(OBzl)4]-OBzl were prepared from the tetra-O-benzylated sugar and Z-Thr-OBzl by the trichloroacetimidate method in the presence of trimethylsilyl trifluoromethane sulfonate. The alpha glycosylated threonine derivatives were converted into Fmoc-Thr(alpha-Glc)-OH and Fmoc-Thr(alpha-Gal)-OH by catalytic hydrogenation followed by acylation with Fmoc-OSu. beta-Glucosylation and beta-galactosylation of threonine were carried out by reacting the proper per-O-acetylated sugar with Z-Thr-OBzl and boron trifluoride ethyl etherate in dichloromethane. Catalytic hydrogenation of the beta-O-glycosylated threonine derivatives followed by acylation with Fmoc-OSu and deacetylation with methanolic hydrazine yielded Fmoc-Thr(beta-Glc)-OH and Fmoc-Thr(beta-Gal)-OH, respectively. The O-glycosylated threonine derivatives were then reacted with H-Lys(Z)-Pro-Arg(NO2)-OBzl in the presence of DCC and HOBt and the resulting glycosylated tuftsin derivatives were fully deblocked by catalytic hydrogenation, purified by HPLC, and characterized by optical rotation, amino acid analysis, and 1H NMR. The beta-galactosylated tuftsin was also prepared by the continuous flow solid phase procedure.

Amino Acid Sequence↗
PubMed1992

Glycosphingolipids in cestodes. Chemical structures of ceramide monosaccharide, disaccharide, trisaccharide and tetrasaccharide from metacestodes of the fox tapeworm, Taenia crassiceps (Cestoda: Cyclophyllidea).

The presence of glycosphingolipids in the metacestodes of the fox tapeworm, Taenia crassiceps, has been established. The normal-phase TLC pattern of the neutral-fraction glycolipids revealed groups of bands corresponding to homologous components of increasing sugar chain length. The three simplest glycolipid components have been isolated and their chemical constitution determined as being of the neogala series: Gal beta 1Cer, Gal beta 6Gal beta 1Cer and Gal beta 6Gal beta 6Gal beta 1Cer. The ceramide tetrasaccharide fraction has been found to consist of a mixture of neogalatetraosylceramide, as an elongation of the neogala series, Gal beta 6Gal beta 6Gal beta 6Gal beta 1Cer and the component Gal alpha 4Gal beta 6Gal beta 6Gal beta 1Cer (both occurring in approximately equimolar proportions). The long-chain bases of the ceramide monogalactoside, digalactoside, trigalactoside and tetragalactosides contain, as well as small amounts of sphingosine, predominantly dihydrosphingosine/phytosphingosine in the approximate ratios 1.7:1, 1.4:1, 1:1 and 2.3:1, respectively. The major ceramide fatty acids have particularly long chains, with hexacosanoic and octacosanoic acids predominating. Upon reverse-phase TCL, the glycolipid components ceramide monogalactoside, digalactoside and trigalactoside were each separable into five component bands. Parent glycolipid components therefore show component band distributions comparable to one another in being governed by similar ceramide constitutions.

Animals↗