High-Resolution, 1H-Nuclear Magnetic Resonance Spectroscopy as a Tool in the Structural Analysis of Carbohydrates Related to Glycoproteins

Accumulation of mannosyl-beta(1----4)-N-acetylglucosamine in fibroblasts and leukocytes of patients with a deficiency of beta-mannosidase

Cultured fibroblasts from two brothers with beta-mannosidosis were shown to accumulate the disaccharide mannosyl-beta(1----4)-N-acetylglucosamine in amounts of 52 and 68 nmol/mg protein. Structural identification of the Man beta(1----4)GlcNAc, isolated by HPLC, was performed by 500-MHz 1H-NMR spectroscopy and sugar composition analysis. Control fibroblasts did not contain a detectable amount of Man beta(1----4)GlcNAc. The disaccharide was also present in leukocytes from these patients, but not in controls, as could be demonstrated by thin-layer chromatography and sugar composition analysis. However, the amounts in leukocytes (5 and 6 nmol/mg protein) were much smaller than those in fibroblasts.

Oligosaccharides at individual glycosylation sites in glycoprotein 71 of Friend murine leukemia virus

Glycoprotein 71 from Friend murine leukemia virus was digested with proteases and the glycopeptides obtained were isolated and assigned, by amino acid sequencing, to the eight N-glycosylated asparagines in the molecule; only Asn334 and Asn341 could not be separated. The oligosaccharides liberated from each glycopeptide by endo-beta-N-acetylglucosaminidase H, or by peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F, were fractionated and subjected to structural analysis by one- and two-dimensional 1H NMR, as well as by methylation/gas-liquid-chromatography/mass-fragmentography. At each glycosylation site, the substituents were found to be heterogeneous including, at Asn334/341 and Asn410, substitution by different classes of N-glycans: oligomannosidic oligosaccharides, mainly Man alpha 1----6(Man alpha 1----3)Man alpha 1----6(Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4GlcNAc beta 1----, were detected at Asn168, Asn334/341 and Asn410. Hybrid species, partially sialylated, intersected and (proximally) funcosylated Man alpha 1----6(Man alpha 1----3)Man alpha 1----6 and Man alpha 1----3Man alpha 1----6 and Man alpha 1----3Man alpha 1----6(Gal beta 1----4GlcNAc beta 1----2Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4GlcNAc beta 1----, were found at Asn12, as previously published [Schlüter, M., Linder, D., Geyer, R., Hunsmann, H., Schneider, J. & Stirm, S. (1984) FEBS Lett. 169, 194-198] and at Asn334/341. N-Acetyllactosaminic glycans, mainly partially intersected and fucosylated NeuAc alpha 2----3 or Gal alpha 1----3Gal beta 1----4GlcNAc beta 1----2Man alpha 1----6(NeuAc alpha 2----6 or NeuAc alpha 2----3Gal-beta 1----4GlcNAc beta 1----2Man alpha 1----3)Man beta 1----4GlcNac beta 1----4GlcNAc beta 1---- with some bifurcation at ----6Man alpha 1----6, were obtained from Asn266, Asn302, Asn334/341, Asn374 and Asn410. In addition, Thr268, Thr277, Thr279, Thr304/309, as well as Ser273 and Ser275, were found to be O-glycosidically substituted by Gal beta 1----3GalNAc alpha 1----, monosialylated or desialylated at position 3 of Gal or/and position 6 of GalNAc.

Carbohydrate analysis of glycoproteins. A review

Many of the products prepared by biotechnological approaches, including recombinant genetic engineering, cell tissue culture, and monoclonal technologies, are glycoproteins. As little as five years ago, glycosylation was believed to play no significant role in the function of glycoproteins. Recent large scale testing of glycoprotein-based pharmaceuticals has indicated that both the extent and type of glycosylation can play a central role in glycoprotein activity. Although methods for compositional and sequence analysis of proteins and nucleic acids are generally available, similar methods have yet to be developed for carbohydrate oligomers and polymers. This review focuses on new, developing methods for the analysis and sequencing of the carbohydrate portion of glycoproteins. Included are: (1) the release of oligosaccharides and hydrolysis of carbohydrate chains using enzymatic and chemical methods; (2) fractionation by LPLC, electrophoresis, HPLC, and lectin affinity chromatography; (3) detection through the preparation of derivatives or by new electrochemical methods; (4) analysis by spectroscopic methods, including MS and high-field NMR; and (5) their sequencing through the use of multiple, well-integrated techniques. The ultimate goal of the analytical approaches discussed is to firmly establish structure and, thus, permit the study of structure-function relationships and eventually to allow the intelligent application of carbohydrate remodeling techniques in the preparation of new glycoproteins.

Primary structure of horse serotransferrin glycans. Demonstration that heterogeneity is related to the number of glycans and to the presence of N-acetylneuraminic acid and N-acetyl-4-O-acetylneuraminic acid

Three serotransferrin variants Tf 2a, Tf 4b and Tf 5b were isolated in an homogeneous form from a preparation of homozygous horse serotransferrin Tf 0. On the basis of the results concerning molecular mass determination and the carbohydrate analysis, it is concluded that the serotransferrin variant Tf 2a contains only one glycan while variants Tf 4b and Tf 5b contain two glycans. The structure of all of the glycans has been established by combining methylation analysis, mass spectrometry and 400-MHz 1H-NMR spectroscopy. From the obtained results, it appears that the two glycans of Tf 5b variant are, like in human serotransferrin, of the N-acetyllactosaminic biantennary type, fully sialylated by two residues of N-acetylneuraminic acid (Neu5Ac; glycan type I). In contrast, in addition to this structure, two N-acetyllactosaminic biantennary isomeric structures named type II-A and type II-B sialylated by one Neu5Ac residue and one N-acetyl-4-O-acetylneuraminic acid [Neu(4,5)Ac2] residue located either at Gal6 or 6' and one N-acetyllactosaminic biantennary structure (named type III) sialylated by two residues of Neu(4,5)Ac2, were identified in variants Tf 2a and Tf 4b. These results demonstrate that in an homozygous preparation of horse serotransferrin Tf 0, the heterogeneity is dependent, on the one hand, on the nature of the neuraminic acid substituting a N-acetyllactosaminic biantennary structure and, on the other hand, on the number of glycans bound to the polypeptide chain. Moreover, the differences which exist in the molecular mass of 77.5 kDA, 80 kDa and 82 kDa for serotransferrin variants Tf 2a, Tf 4b and Tf 5b, respectively, are not completely explained by the structure and the number of the glycans suggesting that the three variants should also differ in their polypeptide chain.

Carbohydrate structure of recombinant human uterine tissue plasminogen activator expressed in mouse epithelial cells

Recombinant human uterine tissue plasminogen activator (tPA), in part metabolically labeled with [6-3H]glucosamine or [35S]sulfate, was isolated from mouse epithelial cells (C127). Oligosaccharides present were liberated by treatment of tryptic glycopeptides with endo-beta-N-acetylglucosaminidase H or peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F and fractionated by high-performance liquid chromatography. The glycans were characterized by digestion with exoglycosidases, methylation analysis and, in part, by acetolysis and 1H-NMR spectroscopy. Glycopeptides comprising individual glycosylation sites were identified by N-terminal amino acid sequencing. The results demonstrate that recombinant tPA from C127 cells carries at Asn117 oligomannosidic glycans with 5-8 mannose residues as well as small amounts of hybrid-type species. Asn184 is only partially glycosylated and substituted by fucosylated triantennary and small amounts of diantennary N-acetyllactosaminic glycans. Likewise, Asn448 carries predominantly fucosylated triantennary species, in addition to, small amounts of diantennary and tetraantennary oligosaccharides. As a characteristic feature, part of the triantennary glycans at Asn184 and Asn448 contain additional Gal(alpha 1-3) substituents and/or sulfate groups linked to position six of beta-galactosyl residues forming NeuAc(alpha 2-3)[HO3S-6]Gal(beta 1-4) units. Oligosaccharides attached to Asn448 are almost completely substituted by (alpha 2-3)- or (alpha 2-6)-linked sialic acid residues and carry the majority of sulfate groups present. Glycans at Asn184 were found to be less sialylated and sulfated.

Three novel oligosaccharides with the sialyl-Lea structure in human milk: isolation by immunoaffinity chromatography

We have determined the structures of three novel oligosaccharides isolated from human milk using the monoclonal antibody MSW 113. These oligosaccharides were purified by affinity chromatography on a column of the immobilized monoclonal antibody and by high-performance liquid chromatography. From the results of 500-MHz 1H NMR spectroscopy and fast atom bombardment-mass spectrometry, their structures were deduced to be (formula; see text) These oligosaccharides bound to MSW 113 to nearly the same extent as sialyl-Lea hexasaccharide but bound to another sialyl-Lea structure-directed monoclonal antibody, NS 19-9, only weakly.

Novel tri-and tetrasialosylpoly-N-acetyllactosaminyl gangliosides of human placenta: structure determination of pentadeca- and eicosaglycosylceramides by methylation analysis, fast atom bombardment mass spectrometry, and 1H NMR spectroscopy

A series of highly polar neolacto series (poly-N-acetyllactosaminyl) gangliosides were isolated from human placenta tissue and purified by HPLC and preparative HPTLC. Two of these ganglioside fractions (G-12 and G-13) were analyzed by 500-MHz 1H NMR spectroscopy, GC-EIMS, +FAB-MS, and sequential exoglycosidase treatments. Their structures have been identified as being of the repeating N-acetyllactosamine type, multiply branched through GlcNAc beta 1----6/3 linkages, with every nonreducing Gal terminal alpha 2----3-sialosylated, as shown below. These are among the highest molecular weight glycosphingolipids whose detailed oligosaccharide structures are presently known. (formula; see text).

Stimulation of the methylcoenzyme M reduction by uridine-5'-diphospho-sugars in cell-free extracts of Methanobacterium thermoautotrophicum (strain delta H)

The hydrogen-dependent reduction of methylcoenzyme M catalyzed by coenzyme-depleted cell-free extracts of Methanobacterium thermoautotrophicum was stimulated by micromolar concentrations of a UDP-disaccharide present in the organism. The compound was isolated and identified as UDP-1-O-alpha-D-2-acetamido-2-deoxyglucopyranose (UDPGlcpNAc) glycosidically linked to 2-acetamido-2-deoxymannopyranosyluronic acid. Maximal stimulation was observed when both the UDP-disaccharide and mercaptoheptanoylthreonine phosphate were present in the reaction mixtures. The UDP derivative isolated was not specific in its action: other UDP-sugars tested in micromolar concentrations stimulated the methylcoenzyme M reduction to the same extent. The activated sugars presumably substitute for ATP, which is usually required in much higher concentrations to activate the methylcoenzyme M reductase system.

Presence of fucosylated triantennary, tetraantennary and pentaantennary glycans in transferrin synthesized by the human hepatocarcinoma cell line Hep G2

Transferrin synthesized by a human hepatocellular carcinoma cell line Hep G2 (called Hep G2 transferrin) was purified from culture media by immunoaffinity chromatography on a rabbit anti-(human serotransferrin) IgG column. The eluted transferrin was then resolved into five peaks on a cation-exchange column using the fast protein liquid chromatography system. The major fraction, named Hep G2 transferrin fraction C, having a molecular mass of 82.5 kDa was found to be homogeneous in polyacrylamide gel electrophoresis and in concanavalin-A-affinity crossed immunoelectrophoresis. A comparative analysis of the molar carbohydrate composition of normal human serotransferrin and of Hep G2 transferrin fraction C shows an increase in the latter in the number of galactose and N-acetylglucosamine residues and in the presence of fucose, which is absent in normal transferrin. By a combination of methylation analysis and NMR spectroscopy, the primary structure of the oligosaccharide alditols released from Hep G2 transferrin fraction C by reductive alkaline cleavage has been established as triantennary, tetraantennary and pentaantennary N-acetyllactosaminic structures with fucose residues (alpha 1-3)-linked to peripheral N-acetylglucosamine residues. These results indicate that the increase in the number of antennae in transferrin glycans synthesized by the hepatocarcinoma cell line is much more pronounced than in liver diseases such as alcoholic cirrhosis and that, in addition, the malignant transformation of human liver induces the presence of fucose.

Primary structure of the major O-glycosidically linked carbohydrate unit of human von Willebrand factor

A reduced tetrasaccharide chain was obtained from human von Willebrand factor (vWF) by mild alkaline borohydride treatment. The purification of this O-glycosidically-linked oligosaccharide was achieved by serial affinity chromatography on immobilized concanavalin A and Lens culinaris agglutinin and finally gel filtration. Its structure was determined by a combination of methylation studies and 500 MHz 1H-NMR spectroscopy to be: NeuAc(alpha 2-3)Gal(beta 1-3)[NeuAc(alpha 2-6)]GalNAc-ol.

Structural analysis of the carbohydrate chains of a mouse monoclonal IgM antibody

A mouse monoclonal IgM antibody, directed against human blood group B determinant, was isolated from hybridoma culture growth medium. Chemical analysis indicated presence of N- and O-linked oligosaccharides. The N- and O-linked carbohydrate chains were liberated using two different conditions of reductive alkaline degradation. Structural analysis was carried out on the isolated chains using chemical analysis, 500-MHz 1H-NMR spectroscopy and fast-atom-bombardment mass spectrometry. The following composite structures of the N-linked chains were found: (formula; see text) where R = OH for biantennary structures and R = Neu5Ac alpha 2-3Gal beta 1-4 GlcNAc beta 1- or Neu5Ac alpha 2-3Gal beta 1-3[Neu5Ac alpha 2-6]GlcNAc beta 1- for triantennary structures. The O-linked oligosaccharides, found in the light chains, were shown to have the structure Neu5Ac alpha 2-3Gal beta 1-3GalNAc. The native IgM antibody could be separated on a concanavalin-A-Sepharose column into two subfractions, differing in the presence of a high-mannose-type oligosaccharide.

Protein glycosylation defects in the Saccharomyces cerevisiae mnn7 mutant class. Support for the stop signal proposed for regulation of outer chain elongation

Total cell mannoprotein was isolated from Saccharomyces cerevisiae X2180 mutants that have defects in elongation of the outer chain attached to the N-linked core oligosaccharides (mnn7, mnn8, mnn9, and mnn10) (Ballou, L., Cohen, R. E., and Ballou, C. E. (1980) J. Biol. Chem. 255, 5986-5991). Comparison of the oligosaccharides released by endoglucosaminidase H digestion confirmed that the mnn9 mutation eliminates all but two mannoses of the outer chain, whereas the mnn8 and mnn10 strains produce outer chains of variable but similar lengths. The isolate designated mnn7 was found to be allelic with mnn8. Haploid mutants of the type mnn8 mnn9 or mnn9 mnn10 had the mnn9 phenotype, which established that the mnn9 defect is dominant and presumably acts at a processing step prior to the steps affected by mnn8 and mnn10. Analysis of the mnn1 mnn2 mnn10 oligosaccharides revealed that the heterogeneous outer chain contained 6-16 alpha 1----6-linked mannose units and each was terminated by a single alpha 1----2-linked mannose unit, whereas the core lacked one such unit that was present in the mnn9 oligosaccharide. The results are consistent with and support the hypothesis (Gopal, P. K., and Ballou, C. E. (1988) Proc. Natl. Acad. Sci. U.S.A. 84, 8824-8828) that addition of such a side-chain mannose unit is associated with termination of outer chain elongation in these mutants and may serve as a stop signal that regulates outer chain synthesis in the parent wild-type strain.

Recombinant human erythropoietin produced by Namalwa cells

To establish a practical exogenous gene expression system in human cells, a cDNA coding for human erythropoietin (EPO) was expressed in human B-lymphoblastoid Namalwa cells. The Namalwa-derived recombinant EPO was purified from the culture fluid by a simple three-step procedure. The Namalwa EPO showed an equivalent activity in vivo to that of human urinary EPO. Oligosaccharide structure analyses suggested that almost all N-linked oligosaccharide chains of Namalwa EPO are shared by urinary EPO. The two major N-linked oligosaccharides of Namalwa EPO were fucose-containing tetraantennary and fucose-containing triantennary structures.

Structures of O-glycosidically linked oligosaccharides isolated from human meconium glycoproteins

The structure of the major O-glycosidically linked neutral and acidic oligosaccharides isolated from human meconium glycoproteins were established. Neutral and acidic oligosaccharides were released by alkaline borohydride treatment, purified by Biogel P-6 and fractionated by high-performance liquid chromatography. This approach resulted in 50 neutral and 30 acidic oligosaccharides. The present study reports the primary structural analysis of five neutral oligosaccharides, ten monosialylated oligosaccharides, one monosialylated monosulfated oligosaccharide and three disialylated oligosaccharides, by permethylation, fast-atom-bombardment mass spectrometry analysis and 400-MHz 1H-NMR spectroscopy. The following structure have not been described previously: (formula; see text) The intestinal glycoproteins of human meconium are characterized as high molecular mass compounds with numerous carbohydrate chains of the mucin type. These mucins are a rich source of carbohydrate structures which express multiple blood group activities and occur as membrane-associated antigens, recognized by hybridoma antibodies [1-4]. A previous study [5] described the structure of fifteen free oligosaccharides derived from catabolism of O- and N-glycans accumulating in new born meconium. In the same group [6] the research has been extended to glycoasparagines with the description of thirteen of them by high resolution 1H-NMR spectroscopy analysis. From O-glycosidically linked glycoproteins, further studies [7] established the structures of nine major monosaccharides to tetrasaccharides obtained after mild acid hydrolysis and base-borohydride degradation from meconium samples of group O secretors. These oligosaccharides were derived from meconium glycopeptides which had been depleted of I- and i-antigen activities. Recently [8], neutral and acidic oligosaccharide-alditols obtained by alkaline borohydride degradation of human meconium glycoproteins have been separated by HPLC on an anion-exchange column. The neutral fraction was further purified by normal-phase and reversed-phase chromatography while acidic fractions were fractionated only by normal-phase chromatography. Thus, we have isolated several low molecular mass oligosaccharides of different size and composition and also isomers which vary in linkage position or anomer configuration. Using methylation analysis, 1H-NMR spectroscopy and fast-atom-bombardment mass spectrometry (FAB-MS), we propose the primary structure for 19 major oligosaccharides.

Computer-assisted structural analysis of polysaccharides with an extended version of CASPER using 1H- and 13C-n.m.r. data

The computer program CASPER, used in the structural analysis of polysaccharides composed of repeating units, has been extended. The extended version uses either unassigned 1H- or 13C-n.m.r. chemical shifts or the complete unassigned C,H-correlation spectrum, and can predict the structure of linear and branched oligo- and poly-saccharides. The number of possible structures, consistent with sugar and methylation analysis, can be decreased by the use of 1JC,H and 3JH,H values. The database, which contains 1H- or 13C-n.m.r. chemical shift data for monosaccharides and 1H- or 13C-glycosylation shifts for all types of glycosidic linkages obtained by combination of the monosaccharides, has been increased and now also contains correction values for sugar residues present in branch-point regions. The program has been tested on four polysaccharides of known structure but with different degrees of complexity. For three polysaccharides, the correct structure was suggested; for the fourth, two structures were consistent with the n.m.r. data, one of them being correct.

N-acetylglucosaminyltransferase III, IV and V activities in Novikoff ascites tumour cells, mouse lymphoma cells and hen oviduct. Application of a sensitive and specific assay by use of high-performance liquid chromatography

A specific and fast method for the determination of N-acetylglucosaminyltransferase III, IV and V activity in one assay is described. The method is based on the separation by HPLC of the three transferase products formed from the common acceptor oligosaccharide substrate GlcNAc beta 1----2Man alpha 1----3(GlcNAc beta 1----2Man alpha 1---- 6)Man beta 1----4GlcNAc. Assays are not interfered with by substances that result from enzymatic or chemical breakdown of the donor substrate UDP-[14C]GlcNAc. Using this assay system N-acetylglucosaminyltransferase III, IV and V activities were estimated in Novikoff ascites tumour cells, mouse lymphoma BW 5147 cells and hen oviduct.

O-mannosylation of recombinant human insulin-like growth factor I (IGF-I) produced in Saccharomyces cerevisiae

A glycosylated form of recombinant human insulin-like growth factor I (IGF-I) expressed in Saccharomyces cerevisiae was shown to contain mannose as the only carbohydrate constituent. All oligosaccharide chains of the glycoprotein could be released by mild alkaline treatment, and separated from the protein by gel-permeation chromatography on Bio-Gel P-2. The structures of these O-linked carbohydrate chains were determined by 500-MHz 1H-NMR spectroscopy, affording the disaccharide Man alpha 1-2Man as the major component and the tetrasaccharide Man alpha 1-3Man alpha 1-2Man alpha 1-2Man as a minor component. Reference oligosaccharides were prepared from mannoproteins released from the cell wall of S. cerevisiae X2180 (alpha-wild type). In addition to previously reported structures, ranging from mannose to mannotetraose, the pentasaccharide Man alpha 1-3Man alpha 1-3Man alpha 1-2Man alpha 1-2Man was identified in the cell wall mannoprotein.

N-linked oligosaccharide changes with oncogenic transformation require sialylation of multiantennae

Glycopeptides derived from NIH 3T3 fibroblasts and these cells transformed by transfection with human DNA containing oncogene H-ras were analyzed by 500-MHz 1H-NMR spectroscopy and binding to immobilized lectins. The cells were metabolically labeled with D-[3H]glucosamine or L-[3H]fucose and the glycopeptides included in Bio-Gel P-10 (Mr 5000-3500) were separated into neutral and charged fractions on DEAE-cellulose. The major portion (80%) of these [3H]fucose glycopeptides from the non-transformed NIH 3T3 fibroblasts were neutral or contained one or two charged residues, whereas 90% of the glycopeptides from the transformed cells contained two or more charged residues. The structure of the predominant neutral glycopeptide from the non-transformed NIH 3T3 cells was determined by 1H-NMR spectroscopy to be tetraantennary containing terminal Gal alpha 1----3. (formula; see text) This structure was verified by binding to the immobilized alpha-Gal-specific lectin, Griffonia simplicifolia I and leukoagglutinating phytohemagglutinin from Phaseolus vulgaris (L-PHA), which binds certain tri- or tetraantennary glycopeptides. In contrast, the structure derived by NMR spectroscopy of one of the predominant charged glycopeptides from the transformed cells was triantennary containing terminal NeuNAc alpha 2----3 in addition to Gal alpha 1----3. (formula; see text) In attempting to verify this structure by lectin-binding properties it was found that removal of NeuNAc alpha 2----3 reduced the affinity to L-PHA - agarose. The other major glycopeptides of the transformed cells which were more charged also cotained NeuNAc alpha 2----3 but no NeuNAc alpha 2----6 or Gal alpha 1----3. A tentative structure was proposed for the major glycopeptide of the first charged class from NIH 3T3 cells on the basis of lectin-binding properties and the NMR spectrum which showed, in addition to NeuNAc alpha 2----3, the presence of NeuNAc alpha 2----6 and Gal alpha 1----3. On the basis of the NMR spectrum and other results, it is concluded that the presence of tetraantennary oligosaccharides are not sufficient for the transformed oligosaccharide phenotype. Rather, the tri- or tetraantennae must be sialylated in alpha 2----3 linkage, on more than one antennae, when properties of transformation are expressed in NIH 3T3 cells. Prior to transformation the tetraantennary oligosaccharides of these cells are terminated in alpha-Gal residues, whereas after transformation alpha-Gal residues appear to be replaced by NeuNAc alpha 2----3.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of alkaline borohydride treatment on N-linked carbohydrates of glycoproteins

The effects of treatments of the glycoprotein ribonuclease-B, the proteins ribonuclease-A and myoglobin, and the glyco-amino acid GlcNAc beta(1-N)Asn with alkali, alkaline sodium borohydride, and aqueous sodium borohydride were systematically studied as a function of the concentration of the reagents, the temperature, and the length of the treatment. High-field 1H-NMR spectroscopy, chromatographic methods and amino-acid analysis were used to characterize products of the treatments of the various compounds. Our results indicate that mild alkaline borohydride treatment, as well as aqueous borohydride treatment alone, is capable of extensively degrading polypeptides and of partially releasing the N-linked glycans from ribonuclease-B. Initially, glycopeptides are produced, the peptide portion of which consists of several amino acids, which are further hydrolyzed to yield a mixture of glyco-asparagines and oligosaccharide-alditols in the ratio of approximately 4:1. Strong alkaline borohydride treatment of ribonuclease-B is capable of completely releasing the N-linked carbohydrates as oligosaccharide-alditols.

Analysis of N-acetyl-4-O-acetylneuraminic-acid-containing N-linked carbohydrate chains released by peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F. Application to the structure determination of the carbohydrate chains of equine fibrinogen

The carbohydrate chains of equine fibrinogen were enzymatically released by peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F. The oligosaccharides obtained were fractionated by a combination of FPLC and HPLC and analyzed by 500-MHz 1H-NMR spectroscopy. Four monosialo and four disialo diantennary N-acetyllactosamine type of carbohydrate chains occur: (formula; see text)

Carbohydrate structure of glycoprotein 65 encoded by the polycythemia-inducing strain of Friend spleen focus-forming virus

The secondary envelope-gene product, glycoprotein 65 (gp65), of the polycythemia-inducing variant of Friend spleen focus-forming virus (F-SFFVp) was isolated from F-SFFVp-infected normal rat kidney cells cultivated in the presence or absence (-Glc) of glucose. Oligosaccharide side chains present were sequentially liberated by treatment of tryptic glycopeptides with endo-beta-N-acetylglucosaminidase H and peptide N-glycosidase F and fractionated by high-performance liquid chromatography. The glycans were characterized by digestion with exoglycosidases, by chromatographic comparison with oligosaccharide standards and by methylation analysis. The results demonstrate that gp65 contains oligomannosidic, hybrid and N-acetyllactosaminic glycans. The oligomannosidic glycans represent the same partially glucosylated species with six to nine mannose residues present in F-SFFVp gp52, the biosynthetic precursor of gp65 [Strube, K.-H. Schott, H.-H. and Geyer, R. (1988) J. Biol. Chem. 263, 3762-3771]. Oligosaccharides of the hybrid type were found to comprise one sialylated lactosamine unit and three or four alpha-linked mannose residues. Analysis of the N-acetyllactosaminic glycans revealed that gp65 carries fucosylated, partially sialylated bi-antennary, tri-antennary and tetra-antennary oligosaccharides, in addition to incomplete species. The glycosylation of gp65(-Glc) is characterized by the presence of oligomannosidic glycans with five to nine mannose residues, similar hybrid-type species and by increased amounts of incomplete N-acetyllactosaminic oligosaccharides, a decrease in sialylation and the lack of tetra-antennary species.

Primary structure of an N-linked sugar chain derived from glucoamylase of Rhizopus niveus

The primary structure of the N-linked sugar chain of Rhizopus niveus glucoamylase (major component) was investigated. The carbohydrate moiety was released from the polypeptide backbone by Flavobacterium sp. endo-beta-N-acetylglucosaminidase digestion. Studies using the method of exoglycosidase digestion of the fluorescent pyridylamino derivative, gel-permeation chromatography on Bio-Gel P-4 and 400-MHz 1H-NMR spectroscopy revealed that the most abundant structure is (Man)8-GlcNac-ol.

Interactions of concanavalin A with asparagine-linked glycopeptides. Structure/activity relationships of the binding and precipitation of oligomannose and bisected hybrid-type glycopeptides with concanavalin A

We have recently demonstrated that certain oligomannose and bisected hybrid-type glycopeptides are bivalent for concanavalin A (ConA) binding and that they can precipitate the lectin [Bhattacharyya, L., Ceccarini, C., Lorenzoni, P & Brewer, C. F. (1987) J. Biol. Chem. 262, 1288-1293]. Two protein-binding sites on each glycopeptide were identified: one on the alpha(1-6) arm of the core beta-mannose residue which binds with high affinity (primary site); the other on the alpha(1-3) arm of the core beta-mannose residue which binds with lower affinity (secondary site). In the present study, we have investigated the relationship between the structures of the primary sites of oligomannose-type glycopeptides and their affinities for ConA. Two mechanisms of binding at the primary sites of oligomannose-type glycopeptides have been identified which account for the 3000-fold increase in affinity of a Man9 glycopeptide relative to that of methyl alpha-D-mannopyranoside. Changes in the structures and affinities of both the primary and secondary sites are observed to influence the precipitation activities of the glycopeptides. These findings have important consequences for the specificity of ConA binding in solutions containing mixtures of the carbohydrates.

Conformational analysis of the sialyl alpha(2----3/6)N-acetyllactosamine structural element occurring in glycoproteins, by two-dimensional NOE 1H-NMR spectroscopy in combination with energy calculations by hard-sphere exo-anomeric and molecular mechanics force-field with hydrogen-bonding potential

The conformation is described of the sialyl alpha(2----3/6)N-acetyllactosamine structural element, frequently occurring in glycoproteins. NOE spectroscopy of NeuAc alpha(2----3)Gal beta(1----4)GlcNAc beta(1----N)Asn and NeuAc alpha(2----6)Gal beta(1----4)GlcNAc beta(1----N)Asn is presented and for each glycosidic linkage, except for the alpha(2----6)-linkage, a number of interglycosidic NOEs are measured. The analysis of these effects is performed using a full relaxation matrix. Analysis of intraresidue NOEs provides a calibration of the calculation method. Hard-sphere exo-anomeric (HSEA) energy calculations indicate a single conformation for the beta(1----4)-linkage in both compounds, both being consistent with the NOE data. HSEA and molecular-mechanics force-field with hydrogen-bonding potential energy calculations both indicate the existence of three preferred conformations for the alpha(2----3)-linkage. The analysis of the NOE spectra are consistent with a distribution over two or three of these conformations; by combination with the energy diagram for this linkage the existence of onyl a single conformation can be excluded. The NOE spectrum of the compound with the alpha(2----6)-linkage indicates a gt orientation for the Gal C-6 hydroxymethyl group. On this basis, the HSEA energy calculations for the alpha(2----6)-linkage indicate an extended low-energy surface with a number of preferred conformations. The absence of NOEs across this linkage is interpreted in terms of a non-rigid, but overall folded conformation of the NeuAc alpha(2----6)Gal beta(1----4)GlcNAc beta structural element. This provides an explanation for the shift effects induced by alpha(2----6) attachment of NeuAc to the N-acetyllactosamine unit.

A detailed study of the periodate oxidation of sialic acids in glycoproteins

Periodate oxidation of terminal N-acetyl- and N-glycoloylneuraminic acid residues in the mucins from edible bird nest substance and pig submandibular gland, respectively, can be carried out under conditions which exclusively give rise to the formation of the C-7 analogues of these sialic acids. In contrast, the C-8 compounds can be obtained in a maximum yield of about 40%. Under identical conditions, N-glycoloylneuraminic acid is oxidized about 1.5 times faster than the N-acetylated derivative. After release of the sialic acids by acid hydrolysis, the characterization of the oxidation products was carried out by TLC, by GLC and GLC-MS of the corresponding pertrimethylsilyl derivatives, and by 500-MHz 1H-NMR spectroscopy. In addition, molar response factors for GLC analysis and extinction coefficients in the orcinol/Fe3+/HCl assay were determined.

Binding and precipitating activities of Erythrina lectins with complex type carbohydrates and synthetic cluster glycosides. A comparative study of the lectins from E. corallodendron, E. cristagalli, E. flabelliformis, and E. indica

Erythrina lectins possess similar structural and carbohydrate binding properties. Recently, tri- and tetra-antennary complex type carbohydrates with non-reducing terminal galactose residues have been shown to be precipitated as tri- and tetravalent ligands, respectively, with certain Erythrina lectins [Bhattacharyya L, Haraldsson M, Brewer CF (1988) Biochemistry 27:1034-41]. The present work describes a comparative study of the binding and precipitating activities of four Erythrina lectins, viz., E. corallodendron, E. cristagalli, E. flabelliformis, and E. indica, with multi-antennary complex type carbohydrates and synthetic cluster glycosides. The results show that though their binding affinities are very similar, the Erythrina lectins show large differences in their precipitating activities with the carbohydrates. The results also indicate significant dependence of the precipitating activities of the lectins on the core structure of the carbohydrates. These findings provide a new dimension to the structure-activity relationship of the lectins and their interactions with asparagine-linked carbohydrates.

Malignant cell glycoproteins and glycolipids

The cell surface is involved in cell growth and division, cell-cell interaction, communication, differentiation and migration, and other processes likely to be involved in malignant transformation and/or the metastatic spread of cancer. Although there are many alterations of glycoproteins and glycolipids on the malignant cell surface, it is unclear whether these alterations are epiphenomena or an integral part of the malignancy process. This article reviews the recent literature and some earlier studies relevant for understanding emerging concepts and trends with respect to malignant cell glycoconjugates. Emphasis is on structural alterations of the carbohydrate portions of malignant cell glycoproteins and glycolipids and on the enzymes (glycosyltransferases and glycosidases) involved in their metabolism. Practical applications derived from malignant cell glycoconjugate studies are discussed briefly with respect to the diagnosis, staging, monitoring, and treatment of malignant disease. The review concludes by indicating which research areas on malignant cell glycoconjugates are likely to be fruitful in increasing our basic understanding of, and ability to deal effectively with, malignant disease.

Assignment of the 1H- and 13C-NMR spectra of eight oligosaccharides of the lacto-N-tetraose and neotetraose series

The assignment of the 13C- and 1H-NMR spectra of eight oligosaccharides of the lacto-N-tetraose and neotetraose series was obtained from homonuclear and heteronuclear correlation spectroscopy. These analyses were performed on the following compounds: 1. Gal beta 1-3GlcNAc beta 1-3Gal beta 1-4Glc; 2. NeuAc alpha 2-3Gal beta 1-3GlcNAc beta 1-3Gal beta 1-4Glc; 3. Gal beta 1-3[NeuAc alpha 2-6]GlcNAc beta 1-3Gal beta 1-4Glc; 4. NeuAc alpha 2-3Gal beta 1-3[NeuAc alpha 2-6]GlcNAc beta 1-3Gal beta 1-4Glc; 5. NeuAc alpha 2-3Gal beta 1-3[Fuc alpha 1-4]GlcNAc beta 1-3Gal beta 1-4Glc; 6. Fuc alpha 1-2Gal beta 1-3[NeuAc alpha 2-6]GlcNAc beta 1-3Gal beta 1-4Glc; 7. Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc; 8. NeuAc alpha 2-6Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc.