María N. Mazzini

The galactomannan system from the endosperm of the seed of Gleditsia triacanthos

Abstract The galactomannan system from the endosperm of the seed of Gleditsia triacanthos is composed of four water-soluble galactomannans having a narrow range of distribution of sugar compositions. Nevertheless, molecular-weight and possible chain-distribution heterodispersion were observed. All of the galactomannan fractions obtained by fractional extraction and further stepwise precipitation with ethanol contained small proportions of xylose and arabinose, and their methylation analysis suggests that minor amounts of lateral chains are ended by arabinofuranose or xylopyranose residues. The variation of the rotations of the galactomannan fractions in solvents of increasing chaotropic power agrees with the suggestion that, in aqueous solution, these molecules exist in an extended, ribbon-like conformation. These entropically unfavorable conformations would be promoted by the spontaneous, noncovalent, and ordered binding of the molecules, producing lower free-energy aggregates; further interactions between these aggregates form gel networks that are maintained in solution by the galactose lateral chains. Methylation analysis shows that the galactomannans have the structure accepted for these polysaccharides. Only minor deviations from this structure were found, but even if they have minor importance as far as the primary structure of the polysaccharide is concerned, they could be important in determining the secondary and tertiary structures and, consequently, in the formation of aggregates and gel networks.

Isolation, partial characterization and biological activity of mannosyl glycopeptides from seminal plasma

Affinity chromatography on Concanavalin-A Sepharose, followed by gel filtration and hydrophobic interaction chromatography, permits the isolation of low molecular weight N-glycosidically linked oligomannosidic glycopeptides (MGp) from the autoproteolysis products of human seminal plasma. The monosaccharide composition of MGp showed only mannose, N-acetylglucosamine and a small amount of galactose. Structural studies were carried out by methylation analysis and chromium trioxide oxidation, and results were consistent with the structures accepted for high-mannose N-glycans. MGp was capable of inhibiting the sperm acrosomal exocytosis mediated by sperm-surface receptors. These data suggest that MGp act as a “decapacitation” factor preventing premature sperm exocytosis.

Affinity chromatography on concanavalin A-Sepharose of antigenic fractions of human seminal plasma.

Elution diagrams obtained on affinity chromatography show that the antigenic fractions of human seminal plasma studied, namely (a) the non-dialyzable components of human seminal plasma and (b) its trichloroacetic acid-soluble fraction, (c) the trichloroacetic acid-soluble fraction of whole human seminal plasma and (d) the pronase digested human seminal plasma, are complex mixtures of glycoproteins with minor amounts of polysaccharides. Some of these glycoproteins contain significant percentages of carbohydrates while others contain only trace amounts. Most of the glycoproteins carry non-reducing end-chain groups comprising alpha-D-glucopyranosyl, alpha-D-mannopyranosyl or sterically related residues.

PROTEOLYTIC RELEASE AND PARTIAL CHARACTERIZATION OF HUMAN SPERM-SURFACE GLYCOPEPTIDES

Sperm-surface glycopeptides were obtained from intact sperm membranes after proteolytic release by different enzymatic treatments such as autoproteolysis, trypsin, papain and pronase. Glycopeptides were isolated, their properties and composition were examined, and their monosaccharide and amino acid constituents were characterized. The monosaccharides identified were fucose, mannose, galactose, N-acetylglucosamine, and N-acetylgalactosamine, which form part of more than one type of oligosaccharide units. Autoproteolytic treatment mainly provided O-glycosidic type oligosaccharides, while a mixture of O- and N-glycosidic oligosaccharides was obtained in variable proportions when treated with trypsin, papain or pronase. The highest degree of peptide cleavage was obtained with pronase. Despite the higher yields reached with trypsin, these glycopeptides contain the lowest percentage of oligosaccharide chains. Proteolytic treatment provides a simple, rapid procedure for the isolation of glycopeptides from the sperm surface.

The determination of fucose in complex natural products

Abstract The actual fucose content of a glycoprotein or a polysaccharide can be determined without previous hydrolysis of the samples by extrapolating to zero time the curve obtained by plotting the amount of fucose against time of heating in sulphuric acid solution in the determination. Evidence is presented which indicates that fucose is not degraded by the acid treatment but by reaction with other compounds produced in the acid reaction medium.