[Complete structure of glycopeptides isolated from IgG immunoglobulins of cow colostrum]

Primary structure of the N-glycosidically linked sialoglycans of secretory immunoglobulins A from human milk

The alkali-stable sialoglycopeptides of secretory immunoglobulins A from human milk have been separated from the alkali-labile glycopeptides by gel filtration and from the asialoglycopeptides by ion-exchange chromatography. The structures of five of them have been determined on the basis of the results obtained by methylation analysis, mass spectrometry and 360 MHz 1H-NMR spectroscopy. For glycopeptide B, the following structure has been found: (formula; see text) The other glycopeptides can be considered as extensions of this structure. The following extensions to Gal-6' are proposed: NeuAc(alpha 2-6) (glycopeptide A), Gal(beta 1-3) (glycopeptide D) and Fuc(alpha 1-6) (glycopeptide E). Furthermore, in glycopeptide C a fucose residue in (alpha 1-3) linkage to GlcNAc-5' could be traced.

Cell-associated glycosaminoglycans of human teratocarcinoma-derived cells of line PA 1

Human teratocarcinoma-derived cells of line PA 1, which are capable of differentiating in vitro [Zeuthen, J. et al. (1980) Int J. Cancer, 25, 19-32], incorporate label from radioactive sulfate and/or glucosamine into several large-sized glycosaminoglycans including hyaluronate, chondroitin sulfate/dermatan sulfate co-polymers, heparan sulfate and keratan-sulfate-like molecules. All these polysaccharide fractions were identified by specific degradation methods. The labeled hyaluronate was degraded into a mixture of unsaturated octa-, hexa- and tetra-saccharides by a treatment with Streptomyces hyaluronidase (EC 4.2.2.1). The chondroitin sulfate/dermatan sulfate co-polymers were cleaved with chondroitin AC lyase (EC 4.2.2.5) into unsaturated disaccharides and a series of unsaturated oligosaccharides; the latter were degraded by a treatment with chondroitin ABC lyase (EC 4.2.2.4) into unsaturated disaccharides. Heparan sulfate was degraded with nitrous acid into free inorganic [35S]sulfate and a series of [35S]sulfate-labeled oligosaccharides and/or glycopeptides. The keratan-sulfate-like molecules were hydrolyzed by a treatment with endo-beta-galactosidase from Escherichia freundii into a series of distinct [35S]sulfate-labeled oligosaccharides; small oligosaccharides were liberated also from [3H]galactose-labeled molecules. The smallest one of the liberated oligosaccharides was tentatively identified as a sulfated disaccharide.

Semliki Forest virus glycans analyzed by affinity chromatography, hydrazinolysis and paper chromatography

N-acetyl-lactosamine type glycopeptides of Semliki Forest virus were fractionated on concanavalin A-Sepharose, and their oligosaccharides were liberated by hydrazinolysis and analyzed by paper chromatography. Comparison with labeled glycans from reference glycopeptides suggests that the viral N-acetyl-lactosamine type glycans are bi-, tri- and tetra-antennary.

Separation of the integral membrane glycoproteins E1 and E2 of Semliki Forest virus by affinity chromatography on concanavalin A-Sepharose

The membrane glycoproteins E1 and E2 of Semliki Forest virus are of about equal size but can be separated from each other by affinity chromatography on a concanavalin A-Sepharose column in the presence of sodium dodecyl sulfate. The E1 protein eluted like glycopeptides containing two peripheral sugar branches composed of N-acetylglucosamine, mannose, galactose and sialic acid. The E2 eluted like glycopeptides containing only N-acetylglucosamine and mannose.

The molecular size of glycans liberated by hydrazinolysis from Semliki Forest virus proteins

The glycans of well characterized, [6-3H]galactose-labelled glycopeptides, GC-4 from bovine IgG1 as well as GP-V-2 and GP-V-5 from alpha1-acid glycoprotein, were liberated by hydrazinolysis. Molecular weights close to the expected values were observed by gel filtration. Desialated glycans of Semliki Forest virus proteins were likewise liberated by hydrazinolysis and subjected to gel filtration. Metabolically labelled [1-3H]galactose-oligosaccharides of the mixed viral proteins revealed an apparent molecular weight of 1800. The bi-antennary glycan liberated from the reference glycopiptide GC-4 was of 1750 daltons. A mixture of [2-3H]mannose-labelled E1- and E2-proteins of the virus contained L-type glycans of 1800 daltons (formerly called A-type), and M-type glycans of 1200 daltons (formerly called B-type). A fraction of the E3-glycans isolated by affinity chromatography on Concanavlin A-Sepharose showed an average molecular weight of 2150, a value intermediate between the three- and four-antennary glycans liberated from the reference glycopeptides GP-V-5 and GP-V-2. The rest of the E3-glycans were of 1850 daltons, a value close to the bi-antennary GC-4 glycan. We suggest that the comparatively large size of the E3-glycans and the exposed position of E3-proteins on the viral surface may be interrelated.

Properties of a beta-D-mannosidase from Aspergillus niger

The beta-D-mannosidase (beta-D-mannoside mannohydrolase, EC 3.2.1.25) from culture filtrate of Aspergillus niger has been purified in large amounts by fractionation with (NH4)2SO4 and DEAE-cellulose chromatography. The removal of traces of alpha-D-galactosidase was performed on a Sepharose-epsilon-aminocaproyl-galactosylamine column. The final enzyme preparation (specific activity 188 units) has no other glycosidase activity and is judged homogeneous. The enzyme has a molecular weight of 130 000 +/- 5000 and an isoelectric point of 4.7. The amino acid composition of the enzyme is characterized by high proportion of acidic amino acids and no cysteine residues and a single chain structure of the enzyme is suggested. The enzyme shows maximum activity on p-nitrophenyl-beta-D-mannopyrano-side at pH 3.5 and at 55 degrees C. The presence of 80% of beta-sheet structure in the protein and 20.8% of monosaccharides (Gal : 1.3; Man : 7; GlcNAc : 1) could explain this relative high heat stability (up to 2 h at 55 degrees C). Enzyme activity is inhibited by mannose (Ki = 7.85 mM) and the specificity is examined.

Carbohydrates of influenza virus. I. Glycopeptides derived from viral glycoproteins after labeling with radioactive sugars

The carbohydrate moiety of the influenza glycoproteins NA, HA(1), and HA(2) were analyzed by labeling with radioactive sugars. Analysis of glycopeptides obtained after digestion with Pronase indicated that there are at least two different types of carbohydrate side chains. The side chain of type I is composed of glucosamine, mannose, galactose, and fucose. It is found on NA, HA(1), and HA(2). The side chain of type II contains a high amount of mannose and is found only on NA and HA(2). The molecular weights of the corresponding glycopeptides obtained from virus grown in chicken embryo cells are 2,600 for type I and 2,000 for type II. The glycoproteins of virus grown in MDBK cells have a higher molecular weight than those of virus grown in chicken embryo cells, and there is a corresponding difference in the molecular weights of the glycopeptides. Under conditions of partial inhibition of glycosylation, virus particles were isolated that contained hemagglutinin with reduced carbohydrate content. Glycopeptide analysis indicated that this reduction is due to the lack of whole carbohydrate side chains and not to the incorporation of incomplete ones. This observation suggests that glycosylation of the viral glycoproteins involves en bloc transfer of the core sugars to the polypeptide chains.

Structural studies on 2-acetamido-1-N-(4-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine and 2-acetamido-6-O-(alpha-L-fucopyranosyl)-1-N-(4-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine by 360-MHz proton-magnetic-resonance spectroscopy

The 360-MHz proton magnetic resonance spectra of 2-acetamido-1-N-(4-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine (GlcNAcbeta1 leads to Asn) and 2-acetamido-6-O-(alpha-L-fucopyranosyl)-1-N-(4-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine (Fucalpha1 leads to 6GlcNAcbeta1 leads to Asn) in deuterium oxide were completely interpreted. The chemical shifts and coupling constants were refined by simulation of the spectra. By means of an adapted Karplus equation the pyranose ring conformation of the sugars was calculated. The change of the geminal coupling constant J6a,6b in the N-acetylglucosamine residue of Fucalpha1 leads to 6GlcNAcbeta1 leads to Asn with respect to GlcNAcbeta1 leads to Asn is proposed to be characteristic for the (1 leads to 6) glycosidic linkage.