Results-Analysis-Oligosaccharides-Glycoproteins-Method-Characterization-Oligosaccharides-Glycoproteins-i
Standardized intermediates for oligosaccharide synthesis. A convenient preparation of partially protected derivatives of allyl O-beta-D-galactopyranosyl-(1--4)-beta-D-glucopyranoside suitable for chain Preparation and antioxidant activity of Pteridium aquilinum-derived In this study, Pteridium aquilinum-derived oligosaccharides (PAO) were prepared from Pteridium aquilinum polysaccharides by hydrolysis using hydrogen peroxide and their hydroxyl radical scavenging activity was investigated. The hydrolysis process was monitored by the yield of PAO. Factors affecting the hydrolysis of Pteridium aquilinum polysaccharides were investigated by using the response surface methodology, and the optimum hydrolysis conditions were determined as follows time, 69 h; temperature, 562 °C; H2O2 concentration, 3% (vv). The hydrolysates were filtered, concentrated to ~25% (wv), precipitated with 6 volumes of ethanol, freeze-dried, and ground to yield a water soluble and white powder. The sugar content of the product was 96%, and the yield was 59% Nonrandom structural features in the heparin polymer.
Computer simulation studies were used to prepare an ensemble of heparin number chains. 2'-Fucose lactose of these chains was simulated by introducing a specific fraction of terminators, and it closely resembled the experimentally observed polydispersity of a porcine mucosal, glycosaminoglycan heparin. The same percentage of simulated chains contained antithrombin III (ATIII) binding site sequences as are typically found to contain ATIII binding sites using affinity chromatography. Heparin lyase action was then simulated by using Michaelis-Menten kinetics. In one model, heparin chains were constructed from the random assembly of monosaccharide units using the observed mole percentage of each. After simulated depolymerization, the final oligosaccharides formed were compared to the observed oligosaccharide products. The simulation which assumed a random distribution of monosaccharide units in heparin did not agree with experimental observations.
In particular, no ATIII binding site sequences were found in the simulated number chains. The results of this simulation indicate that heparin is not simply a random assembly of monosaccharide units. These results are consistent with the known, ordered biosynthesis of heparin. In a second model, heparin chains were constructed from randomly assembled oligosaccharides at the mole percentage in which each is found in the final product mixture. The action of heparin lyase was then simulated, and the distribution of the oligosaccharide products was measured throughout the simulated time course of the depolymerization reaction. The simulated rate of formation and final concentration of a particular oligosaccharide which contains a portion of heparin's ATIII binding site were similar to those observed experimentally. These results are consistent with the random distribution of ATIII binding sites within glycosaminoglycan heparin.
(ABSTRACT TRUNCATED AT 2 Developmental regulation of asparagine-linked oligosaccharide synthesis in In the preceding report we demonstrated that the expression of two developmentally regulated alpha-mannosidase activities is induced in Dictyostelium discoideum during its differentiation from single-cell amoebae to multicellular organism (Sharkey, D. 2'-fucosyllactose , and Kornfeld, R. (1991) J. Biol. Chem. 266, 18477-18484).
These activities, designated membrane alpha-mannosidase I properties in common with rat liver Golgi alpha-mannosidases I and II, respectively, suggesting that MI and MII may play a role in the processing of asparagine-linked oligosaccharides in developing D. discoideum. In this study we analyzed the structures of the asparagine-linked oligosaccharides synthesized by D. discoideum at various stages of development to determine the timing and extent of asparagine-linked oligosaccharide processing. Cells were labeled with [2-3H] mannose, and then total cellular glycoproteins were digested with Pronase to generate glycopeptides that were fractionated on concanavalin A-Sepharose. Glycopeptides from each fraction were digested with endoglycosidase H, both before and after desulfation by solvolysis, and the released, neutral oligosaccharides were sized by high pressure liquid chromatography. At early stages of development, D.
discoideum contain predominantly large high mannose-type oligosaccharides (Man9GlcNAc and Man8GlcNAc). Some of these are modified by GlcNAc residues attached beta 1-4 to the mannose-linked alpha 1-6 to the beta-linked core mannose (the intersecting position), as well as by fucose, sulfate, and phosphate.
