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At least 469 records · Page 26Linked to original sources
PubMed1986

3-Methoxy-4-(2-nitrovinyl)phenyl glycosides as potential chromogenic substrates for the assay of glycosidases.

Selective glycosidation of 2,4-dihydroxybenzaldehyde with either 2,3,4, 6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide, 2-acetamido-3,4,6-tri-O-acetyl-alpha-D-glucopyranosyl chloride, or 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide afforded the corresponding 4-O-glycosyl derivatives. Subsequent O-methylation, O-deacetylation, and condensation with nitromethane afforded the appropriate beta-glycoside of 3-methoxy-4-(2-nitrovinyl)phenol. The phenol is highly coloured at alkaline pH so that these glycosides may be suitable as chromogenic substrates for the assay of glycosidases.

Chemical Phenomena↗
PubMed1990

Hydrolysis of (1----3)- and (1----2)-beta-D-xylosidic linkages by an endo-(1----4)-beta-D-xylanase of Cryptococcus albidus.

The substrate specificity of an endo-(1----4)-beta-D-xylanase of the yeast Cryptococcus albidus was investigated using a series of methyl beta-D-xylotriosides. In addition to (1----4) linkages, the enzyme could cleave (1----3) and (1----2) linkages adjacent to a (1----4) linkage and further from the non-reducing end of the substrate. The enzyme could hydrolyse a (1----3) linkage that attached a terminal xylopyranosyl group to a (1----4)-linked xylobiosyl moiety. The enzyme did not attack alpha-D-xylosidic linkages. The rate of cleavage of (1----4) linkages was much higher than those of other linkages at 0.5mM substrate, but the rates were comparable at 20mM substrate when transglycosylation reactions also occurred that facilitated degradation of the substrates.

Carbohydrate Conformation↗
PubMed1990

Enzymic synthesis of HexNAc-containing disaccharide glycosides.

The following disaccharide glycosides were obtained from the appropriate donor and acceptor glycosides by employing glycosidases from the mollusc Chamelea gallina as catalysts: alpha-D-Galp-OMe (N-acetyl-alpha-D- galactosaminidase), beta-D-GalpNAc-(1----3)-beta-D-Galp-OMe, beta-D-GlcpNAc-(1----3)-beta-D-Galp-OMe, and beta-D-GlcpNAc-(1----6)-alpha-D-Manp-OMe (N-acetyl-beta-D-hexosaminidase). The regioselectivity of the N-acetyl-beta-D-hexosaminidase-catalysed reactions depended on the anomeric configuration of the acceptor. Thus, alpha-D-Galp-OMe gave beta-D-GlcpNAc- (1----6)-alpha-D-Galp-OMe almost exclusively, whereas beta-D-Galp-OMe gave beta-D-GlcpNAc-(1----3)-beta-D-Galp-OMe and beta-D-GlcpNAc-(1----6)-beta-D-Galp-OMe in almost equal amounts. The isolation of the products by chromatography was straightforward.

Animals↗
PubMed1993

Syntheses of 2-deoxy-2-fluoro mono- and oligo-saccharide glycosides from glycals and evaluation as glycosidase inhibitors.

Several fluorinated oligosaccharides, including 2-deoxy-2-fluoro derivatives of cellobiose, maltose, and maltotriose were synthesized by the action of fluorine or acetyl hypofluorite on the corresponding glycal peracetates. Temperature effects on the stereoselectivities of these reactions were examined. Addition of acetyl hypofluorite to several 2-substituted glycals in the gluco or galacto series gave 2,2-disubstituted arabino- or lyxo-hexose derivatives; 3,4,6-tri-O-acetyl-2-fluoro-D-glucal or the analogous galactal yielded 2-deoxy-2,2-difluoro arabino- or lyxo-hexose peracetates, whereas 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal or the analogous galactal gave 2(R)-2-acetoxy-2-fluoro-arabino- or lyxo-hexose peracetates, respectively. 2-Acetamido-3,4,6-tri-O-acetyl-D-glucal gave 2(R)-2-acetamido-2-acetoxy-3,4,6-tri-O-acetyl-alpha-D-arabino-hexopyrano syl fluoride. 2,4-Dinitrophenyl 2-deoxy-2-fluoro-beta-cellobioside was an inactivator of the exoglucanase from Cellulomonas fimi while 2-deoxy-2-fluoro-alpha-maltosyl and alpha-maltotriosyl fluorides were slow substrates of human pancreatic alpha-amylase and rabbit muscle glycogen debranching enzyme, respectively.

Acetates↗
PubMed1995

A bi-fluorescence-labeled substrate for ceramide glycanase based on fluorescence energy transfer.

An alkyl lactoside containing two different fluorescence probes as an energy donor and an energy acceptor was synthesized as a substrate for ceramide glycanase. n-Pentenyl beta-lactoside was converted into its 4',6'-O-(2-naphthylmethylidene) derivative with subsequent benzoylation of all remaining OH groups. The fully protected lactoside was treated with borane-trimethylamine complex and aluminum chloride in tetrahydrofuran [P.J. Garegg, Pure Appl. Chem., 56 (1984) 845-858] for selective opening of the 4',6'-acetal group to give the 6'-O-(2-naphthylmethyl) derivative in high yield. After O-debenzoylation, the omega-alkenyl group at the reducing end was extended by Michael addition with HS(CH2)2NH2.HCl to provide an amino group at the terminal position. The amino group was then dansylated to give the target lactoside, which has two different fluorescent probes at each end. Excitation at 290 nm (of the 2-naphthyl group) of the bi-fluorescence-labeled lactoside showed emissions at 335 nm (2-naphthyl) and at 540 nm (dansyl). The distance between the naphthyl group and the dansyl group was estimated to be 12 A by the Förster relationship. Digestion of this lactoside with American leech (Macrobdella decora) ceramide glycanase [B. Zhou et al., J. Biol. Chem., 264 (1989) 12,272-12,277] resulted in an increase in the naphthyl emission with a concomitant decrease in the dansyl emission. These changes can be used for continuous monitoring of the ceramide glycanase activity.

Animals↗
PubMed1984

Glycosidic bond rearrangements in isomeric xylobioses by yeast xylan-degrading enzymes.

The cells of Cryptococcus albidus induced for xylan-degrading enzymes are capable of transforming 1,2-beta-xylobiose and 1,3-beta-xylobiose into 1,4-beta-xylobiose, the natural inducer. The conversion involves transglycosylation and hydrolysis catalyzed by beta-xylosidase and beta-xylanase. A probable intermediate of the conversion of 1,2-beta-xylobiose was isolated and identified as a trisaccharide, 4-O-beta-xylopyranosyl-2-O-beta-xylopyranosyl-D-xylopyran ose. The trisaccharide is cleaved by purified endo-1,4-beta-xylanase of C. albidus mainly at the 1,2-beta-linkage yielding xylose and 1,4-beta-xylobiose.

Carbohydrate Conformation↗
PubMed1991

Vaccinia-vectored expression of the rubella virus structural proteins and characterization of the E1 and E2 glycosidic linkages.

The maturation of rubella virus (RV) glycoprotein E2 from the single intracellular species (E2i; MW = 40 kDa) to the heterodisperse virion species (E2v; MW = 42 to 47 kDa), was studied by pulse-chase radiolabeling in Vero cells infected with RV or with recombinant vaccinia viruses (VVs) which express the entire RV structural protein open reading frame (VV-CE2E1) or glycoprotein E2 independently (VV-E2). The RV proteins expressed by the recombinant VVs comigrated with authentic RV intracellular proteins. In pulse-chase experiments, performed in both RV- and VV-CE2E1-infected cells, the amount of pulse-labeled E2i was substantially reduced during a 3- to 4-hr chase; during the same chase the amount of pulse-labeled E1 and C did not change. The concomitant appearance of the E2v forms was not observed. In contrast, in VV-E2-infected cells, no reduction in the amount of E2i occurred after as long as a 10-hr chase. Western blots using anti-E2 monoclonal antibodies showed that E2i was the predominant E2 species in cells infected with RV, VV-CE2E1, and VV-E2. However, minor amounts of three discrete species which comigrated within the extent of the E2v smear were also detected in cells infected with all three viruses, indicating that some degree of intracellular processing to E2v did occur. The disappearance of E2i during pulse-chase radiolabeling without the concomitant appearance of detectable E2v and the predominance of this labile form under steady-state conditions as revealed by Western blot analysis suggested that E2i was selectively turned over in both RV- and VV-CE2E1-infected cells. Such turnover was not apparent in VV-E2-infected cells, indicating that association with C and E1 was necessary for turnover to occur. Endoglycosidase digestion experiments and glycan differentiation assays revealed that E2v contained O-linked glycans. The presence of O-glycans on E2v accounted for part of the difference in size between E2v and E2i. Both virion E1 and E2 were found to contain high-mannose, hybrid-type, and complex-type N-glycans. Heterogeneity existed in the extent of processing of these glycans among individual E1 and E2 molecules.

Animals↗