J. Conchie

Soluble lignin-carbohydrate complexes from sheep rumen fluid: their composition and structural features.

Lignin-carbohydrate complexes, isolated from cell-free rumen fluid of sheep, consisted of polyphenolic material in association with carbohydrate (5.5%) and protein (1.8%). No separation of carbohydrate from the other components could be effected. The complexes showed a bimodal distribution of molecular size with the higher-molecular-weight fraction richer in carbohydrate. Methylation analysis indicated a wide range of linkages and a high proportion of terminal sugars. Reducing sugars were found in the complexes, particularly in the low-molecular-weight fraction (approximately 25%), suggesting that ether linkages to the phenolics were also present.

The determination of the individual neutral and amino sugars in carbohydrates.

Abstract An experimental study has been made of procedures for the acid hydrolysis and methanolysis of sugar polymers. Individual neutral and amino sugars in the products were examined by colorimetric methods and by gas-liquid chromatography of the trimethylsilyl derivatives. Quantitative N -acetylation of amino sugars was carried out with dilute acetic anhydride in aqueous acetone (1:1, v/v) on a column of Dowex 1 (CO 3 2− form). Methanolysis was found to be preferable for the release of neutral sugars from glyco-proteins, whereas acid hydrolysis should be employed for amino sugars.

The carbohydrate units of ovalbumin: Complete structures of three glycopeptides

Abstract Three glycopeptides, obtained in quantity from ovalbumin by exhaustive digestion with Pronase and purified by ion-exchange chromatography and gel filtration, had mannose-2-acetamido-2-deoxyglucose-aspartic acid ratios of 5:4:1, 6:2:1, and 5:2:1. The structures of the glycopeptides have been investigated by sequential digestion with purified exo-glycosidases, Smith degradation, and selective acetolysis, and by methylation analysis of the glycopeptides and their degradation products. The resulting data indicated the structures to be α- d -Man p -(1→6)-[α- d - Man p -(1→3)]-α- d -Man p -(1→6)-[β- d -GlcNAc p -(1→4)]-[β- d -GlcNAc p -(1→2)-α- d - Man p -(1→3)]-β- d -Man p -(1→4)-β- d -GlcNAc p -(1→4)-β- d -GlcNAc p →Asn, α- d - Man p -(1→6)-[α- d -Man p -(1→3)]-α- d -Man p -(1→6)-[α- d -Man p -(1→2)-α- d -Man p - (1→3)]-β- d -Man p -(1→4)-β- d -GlcNAc p -(1→4)-β- d -GlcNAc p →Asn, and α- d -Man p - (1→6)-[α- d -Man p -(1→3)]-α- d -Man p -(1→6)-[α- d -Man p -(1→3)]-β- d -Man p -(1→4)- β- d -GlcNAc p -(1→4)-β- d -GlcNAc p →Asn. The glycopeptides had a common-core structure consisting of five mannose and two hexosamine residues, but the two larger glycopeptides were not homologous.

The carbohydrate units of asialo-ovomucoid: Structural features

The structural features of a heterogeneous glycopeptide fraction from asialo-ovomucoid have been investigated by methylation analysis of the fraction and of products obtained at each stage of its sequential degradation with exo-glycosidases. All glycopeptides in the fraction had a common core-structure beta-D-GlcpNAc-(1 leads to 4)-[beta-D-GlcpNAc-(1 leads to 2)]-alpha-D-Manp-(1 leads to 3)-[beta-D-GlcpNAc-(1 leads to 4)]-[beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 4)-beta-D-GlcpNAc leads to Asn. Heterogeneity in the fraction arose from variation in the amount of terminal galactose attached via a hexosaminyl residue to the alpha-D-Manp-(1 leads to 3) residue, and from limited variation in the number of terminal hexosaminyl groups attached to the alpha-D-Manp-(1 leads to 6) residue. One glycopeptide in the fraction contained the unusual feature of two different, triply-substituted mannosyl residues. Other structural features of the glycopeptide are discussed.

The carbohydrate units of asialo-ovomucoid: Their hetero-geneity and enzymic degradation

An ovomucoid variant free from sialic acid has been prepared in a pure state by ion-exchange chromatography on DEAE-cellulose. The purified glycoprotein contained 10-11 residues of mannose, 2-3 residues of galactose, and 21 residues of 2-acetamido-2-deoxyglucose. Glycopeptides have been prepared by exhaustive digestion with Pronase followed by ion-exchange chromatography on Dowex 50 (X2) resin. Three fractions were obtained, all with similar contents of mannose and hexosamine but with various contents of galactose. The sugar-aspartic acid ratios indicated that all of the fractions were heterogeneous, the major fraction having mannose-galactose-hexosamine-aspartic acid ratios of 2.6:0.5:5.8:1.0. Cleavage of asialo-ovomucoid with cyanogen bromide and proteolytic digestion of the isolated fragments gave two heterogeneous glycopeptide fractions of similar composition. Both asialo-ovomucoid and the principal glycopeptide fraction were degraded with beta-D-galactosidase, alpha-D-mannosidase, and beta-N-acetylglucosaminidase singly and in sequence. Removal of much of the carbohydrate from asialo-ovomucoid had no appreciable effect on its anti-tryptic activity. By sequential degradation of the glycopeptide, a pentasaccharide core alpha-D-Man-[alpha-D-Man]-beta-D-Man-beta-D-GlcNAc-beta-D-GlcNAc-Asn was obtained. Other structural features revealed by enzymic degradation are discussed.