J. Montreuil

Structure of the three major sialyl-oligosaccharides excreted in the urine of five patients with three distinct inborn diseases: "I cell disease" and two new types of mucolipidosis.

The urine of five patients with three distinct diseases (I Cell disease and two new types of mucolipidosis) contains sialic acid-rich oligosaccharides in a high amount: 50- to 500-fold the normal. The structure of the major components are as follows: alphaAcNeu(2 leads to 6)betaGal(1 leads to 4)betaGlcNac(1 leads to 2)alphaMan(1 leads to 3)betaMan(1 leads to 4)GlcNac,[alphaAcNeu(2 leads to 6)]betaGal(1 leads to 4)betaGlcNAc(1 leads to 2)alphaMan(1 leads to 3)[betaGal(1 leads to 4)betaGlcNac(1 leads to 2)alphaMan(1 leads to 6)]betaMan(1 leads to 4)GlcNAc and alphaAcNeu(2 leads to 6)betaGal(1 leads to 4)betaGlcNAc(1 leads to 2)alphaMan(1 leads to 3)[alphaAcNeu(2 leads to 6)betaGal(1 leads to 4)betaGlcNAc(1 leads to 2)alphaMan(1 leads to 6)]betaMan(1 leads to 4)GlcNAc. These results suggest that a deficit in alpha-neuraminidase is associated to these three different disorders and that an endo-beta-D-N-acetylglucosaminidase is able to release sialyoligosaccharides by splitting the sialylglycans of glycoproteins.

Etude chimique des mannosides urinaires excrétés au cours de la mannosidose

Summary Mannose-rich oligosaccharides have been isolated from urines of 5 patients with mannosidosis. Their composition and structure were determined. Three of them have been previously described by Norden et al.: α- d -Manp-(1 → 3) β- d -Mapp-(1 → 4) d -GlcNAcp; α- d -Manp-(1 → 2) α- d -Mapp-(1 → 3) β- d -Manp-(1 → 4) d -GlcNAc and α- d -Manp-(1 → 2) α- d -Manp-(1 → 2) α- d -Manp-(1 → 3) β- d -Manp-(1 → 4) d -GlcNAcp, but the four others are new entities: α- d -Manp-(1 → 3) [α- d -Manp-(1 → 2) α- d -Manp-(1 → 2) α- d -Manp-(1 → 6)] β- d -Manp-(1 → 4) GlcNAcp; α- d -Manp-(1 → 2) α- d -Manp-(1 → 3) [α- d -Manp-(1 → 2) α- d -Manp-(1 → 2) α- d -Manp-(1 → 6)] β- d -Manp-(1 → 4) GlcNAcp; [α- d -Manp-(1 → 2)4 α- d -Manp-(1 → 3) [α- d -Manp-(1 → 6)] β- d -Manp-(1 → 4) GlcNAcp and α- d -Manp-(1 → 2)]5 α- d -Manp-(1 → 3) [α- d -Manp-(1 → 6)] β- d -Manp-(1 → 4) GlcNAcp. These structures are related to the glycans of «oligomannosidic type present in numerous glycoproteins. All possess a N-acetylglucosamine residue in terminal reducing position and reinforce the hypothesis of Kobata et al. and Montreuil et al. that catabolism of glycans N-glycosidically linked to the protein moiety begins by the action of a β-endo-N-acetylglucosaminidase.

Characterization of a novel endo-N-acetyl-β-d-glucosaminidase from the culture filtrate of a basidiomycete (Sporotricum dimorphosporum), active on biantennary mono- and asialoglycoasparagines of the N-acetyllactosaminic type

A novel endo-N-acetyl-beta-D-glucosaminidase has been characterized in a culture filtrate from a Basidiomycete. This enzyme hydrolyses biantennary monosialo and asialo-glycoasparagines of the N-acetyllactosaminic type. Endo-N-acetyl-beta-D-glucosaminidase from the Basidiomycete released from different glycoasparagines, beta-GlcNAc-(1 leads to 4)-N[14C] acetyl-Asn, alpha Fuc-(1 leads to 6)-beta-GlcNAc-(1 leads to 4)-N-[14C]acetyl-Asn and oligosaccharides which have been separated by paper and thin-layer chromatography. Determination of the radioactivity of the labeled fragments leads to the conclusion that the biantennary glycoasparagines of the N-acetyllactosaminic type are hydrolyzed after 1 h incubation at 37 degrees, to the extent of 15 per cent for the monosialo; 90 per cent for the asialo; 21 per cent for the asialo-monofucosylated, and 15 per cent for the asialo-difucosylated glycans. Tri- and tetraantennary asialo-glycans of the N-acetyllactosaminic type are not hydrolyzed by this enzyme.

Isolation and characterization of surface glycopeptides from adult rat hepatocytes in an established line

The fractionation of glycopeptides isolated from the surface of an established line of adult rat hepatocytes, after 48 h metabolic labeling with [14C] glucose leads to the demonstration of the presence of two types of glycopeptides: i) O-glycopeptides containing N-acetylneuraminic acid, galactose and N-acetylgalactosamine, ii) N-glycopeptides with mannose, galactose, N-acetylgluosamine, fucose and N-acetylneuraminic acid. The former yield, by alkaline reductive degradation, a trisaccharide: sialyl-galactosyl-N-acetyl-galactosaminitol, a tetrasaccharide : di-sialyl-galactosyl-N-acetyl-galactosaminitol and a small amount of the disaccharide: galactosyl-N-acetyl-galactosaminitol. The latter are alkali-stable and can be divided by ion-exchange chromatography on DEAE-cellulose into i) acidic glycopeptides, not retained on a Concanavalin A-Sepharose column and belonging to the N-acetyllactosaminic type glycopedtides and ii) neutral glycopeptides which can be further fractionated on the Con-A-Sepharose column into non-retained glycopeptides belonging to the N-acetyllactosaminic type, and glycopeptides retained on the Sepharose-Con A column, containing only N-acetylglucosamine and mannose residues and related to the oligomannosidic type glycopeptides.

Analytical and comparative chromatographic maps of oligosaccharides produced by acetolysis and partial acid hydrolysis of glycoprotids.

The authors describe a chromatographic mapping procedure of oligosaccharides present in acetolysates and partial acid hydrolysates of glycopeptides or glycoproteins. Oligosaccharides are first fractionated on charcoal-Celite columns and then identified by paper chromatography. This procedure is sensitive and reproducible and allows to compare the structure of N-glycans and of glycoproteins from various sources.