Primary structure of the asparagine-563-linked carbohydrate chain of an immunoglobulin M from a patient with Waldenstrom's macroglobulinemia. A reinvestigation by 500-MHz H-NMR spectroscopy

Pichia pastoris-produced mucin-type fusion proteins with multivalent O-glycan substitution as targeting molecules for mannose-specific receptors of the immune system

Mannose-binding proteins like the macrophage mannose receptor (MR), the dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) and mannose-binding lectin (MBL) play crucial roles in both innate and adaptive immune responses. Immunoglobulin fusion proteins of the P-selectin glycoprotein ligand-1 (PSGL-1/mIgG(2b)) carrying mostly O-glycans and, as a control, the α1-acid glycoprotein (AGP/mIgG(2b)) carrying mainly N-linked glycans were stably expressed in the yeast Pichia pastoris. Pichia pastoris-produced PSGL-1/mIgG(2b) was shown to carry O-glycans that mediated strong binding to mannose-specific lectins in a lectin array and were susceptible to cleavage by α-mannosidases including an α1,2- but not an α1,6-mannosidase. Electrospray ionization ion-trap mass spectrometry confirmed the presence of O-glycans containing up to nine hexoses with the penta- and hexasaccharides being the predominant ones. α1,2- and α1,3-linked, but not α1,6-linked, mannose residues were detected by (1)H-nuclear magnetic resonance spectroscopy confirming the results of the mannosidase cleavage. The apparent equilibrium dissociation constants for binding of PNGase F-treated mannosylated PSGL-1/mIgG(2b) to MR, DC-SIGN and MBL were shown by surface plasmon resonance to be 126, 56 and 16 nM, respectively. In conclusion, PSGL-1/mIgG(2b) expressed in P. pastoris carried O-glycans mainly comprised of α-linked mannoses and with up to nine residues. It bound mannose-specific receptors with high apparent affinity and may become a potent targeting molecule for these receptors in vivo.

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.

Structural studies of the asparagine-linked sugar chains of two immunoglobulin M's purified from a patient with Waldenström's macroglobulinemia

The structures of the sugar chains present in two human monoclonal IgM molecules purified from the serum of a patient with Waldenström's macroglobulinemia have been determined. The asparagine-linked sugar chains were liberated as oligosaccharides by hydrazinolysis and labeled by reduction with NaB3H4 after N-acetylation. Their structures were studied by serial lectin column chromatography and sequential exoglycosidase digestion in combination with methylation analysis. These two IgM's were shown to contain almost the same sugar chains. The sugar chains were a mixture of a series of high-mannose-type and biantennary complex-type oligosaccharides. The complex-type oligosaccharides contain Man alpha 1----6(+/- GlcNAc beta 1----4)(Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4(Fuc alpha 1----6)GlcNAc as their core and GlcNAc beta 1----, Gal beta 1----4GlcNAc beta 1---- and Neu5Ac alpha 2----6Gal beta 1----4GlcNAc beta 1---- groups in their outer chain moieties.

Determination of the structure of the carbohydrate chains of prostaglandin endoperoxide synthase from sheep

Prostaglandin endoperoxide synthase was isolated from sheep seminal vesicles. Sugar analysis of the glycoprotein revealed the presence of mannose and N-acetylglucosamine only. The carbohydrate moiety was released from the polypeptide backbone by hydrazinolysis. After re-N-acetylation and reduction, the resulting mixture of oligosaccharide-alditols was fractionated on Bio-Gel P-4 and their structures were investigated by 500-MHz1H-NMR spectroscopy. The carbohydrate chains turned out to be of the oligomannoside type containing six to nine mannose residues. The largest and most abundant compound was established to be: (formula; see text) For the smaller structures heterogeneity occurs with respect to the outer alpha(1----2)-linked mannose residues. Furthermore, a small amount of Man6GlcNAc-ol (artefact of the hydrazinolysis procedure) was detected by 1H-NMR spectroscopy and fast atom bombardment mass spectrometry.

Determination of the structure of ovalbumin glycopeptide AC-B by 1H nuclear magnetic resonance spectroscopy at 500 MHz

Three unique, unmodified ovalbumin glycopeptides were separated to homogeneity by high-pressure liquid chromatography. The nuclear magnetic resonance data, at 500 MHz, confirmed the structure of two of the three species and for the first time established the presence of a Man8GlcNAc2Asn glycopeptide in ovalbumin. This compound was a single homogeneous isomeric form out of three possible compounds expected as processing intermediates.

Primary structure of the major glycans of the N-acetyllactosamine type derived from the human immunoglobulins M from two patients with Waldenström's macroglobulinemia

The carbohydrate chains of the pathological human immunoglobulins M from two patients with Waldenström's macroglobulinemia were released by hydrazinolysis. The N-acetyllactosamine-type glycans were obtained by affinity chromatography on concanavalin A and fractionated by high-voltage paper electrophoresis. The primary structure of the major compounds was elucidated on the basis of carbohydrate analysis, methylation analysis, including mass-spectrometry, and 500 MHz 1H-NMR spectroscopy. For both patients, this appeared to be a monosialyl monofucosyl biantennary structure; the compounds differed by the presence of an intersecting N-acetylglucosamine residue.

Oligosaccharides on cathepsin D from porcine spleen

Cathepsin D from porcine spleen contained mannose (3.3%), glucosamine (1.4%), and mannose 6-phosphate (0.08%). Essentially all of the oligosaccharides of cathepsin D could be released by endo-beta-N-acetylglucosaminidase H, pointing to oligomannoside types of structures. Three neutral oligosaccharide fractions, containing 5, 6, and 7 mannose residues, respectively, were isolated by gel permeation chromatography on Bio-Gel P-2. Studies using exoglycosidase digestions and 500-MHz 1H NMR spectroscopy revealed that their structures are [Man alpha 1 leads to 2]0 or 1 Man alpha 1 leads to 6[Man alpha 1 leads to 3]Man alpha 1 leads to 6[Man alpha 1 leads to 2)0 or 1 Man alpha 1 leads to 3]Man beta 1 leads to 4GlcNAc beta 1 leads to 4 GlcNAc. These structures are identical to what have recently been proposed by Takahashi et al. for the major oligosaccharide units of cathepsin D from the same source (T. Takahashi, P. G. Schimidt, and J. Tang (1983) J. Biol. Chem. 258, 2819-2930), except for the occurrence of two isomeric oligosaccharides containing six mannoses. Only a part (3.4%) of the oligosaccharides were acidic, containing phosphates in monoester linkage. The phosphorylated oligosaccharides also consisted of oligomannoside-type chains which were analogous to, but more heterogeneous in size than the neutral oligosaccharides. Cathepsin D was bound to a mannose- and N-acetylglucosamine-specific lectin (mannan-binding protein) isolated from rabbit liver with the Ki value of 5.4 X 10(-6) M.

Methylation analysis of complex carbohydrates in small amounts: capillary gas chromatography-mass fragmentography of methylalditol acetates obtained from N-glycosidically linked glycoprotein oligosaccharides

A version of the methylation analysis of complex carbohydrates by gas chromatography-mass spectrometry of the methylalditol acetates (H. Björndal, C. G. Hellerquist, B. Lindberg, and S. Svensson (1970) Angew. Chem. 82, 643-674) is described. With this version 100- to 500-pmol samples of N-glycosidically linked glycoprotein oligosaccharides may be analyzed. The method is based on the use of capillary columns which allow the separation of all partially methylated alditol acetates potentially obtained from this group of oligosaccharides and on their selective and sensitive detection by mass fragmentography after chemical ionization with ammonia.

Purification and characterization of a beta-N-acetylglucosaminidase from Octopus vulgaris. Determination of specificity by using 360-MHz 1H-NMR spectroscopy

We have purified a beta-N-acetylglucosaminidase from the hepatopancreas of the octopus which we have called beta I. The enzyme was homogeneous as judged by Sephadex column chromatography, isoelectric focusing, non-denaturing gel electrophoresis at two different pH and with sodium dodecyl sulphate/polyacrylamide gel electrophoresis. The native protein has an apparent molecular weight of 120 000 and we can conclude that it is a tetramer made up of two alpha and two beta subunits with apparent Mr of 27 000 and 34 000, respectively. Using NMR spectroscopy we have examined the specificity of beta I and have established that the enzyme hydrolyses the beta 1,4 linkage of N-acetylglucosamine but at only a specific site of the substrates used, two glycopeptides isolated from ovalbumin. To our knowledge this is the first known exoglycosidase which has both linkage and site specificity.

Characterization of the primary structure and the microheterogeneity of the carbohydrate chains of porcine blood-group H substance by 500-MHz 1H-NMR spectroscopy

In blood-group H substance from pig stomach cell linings, carbohydrate structures are known to occur which are O-glycosidically linked via GalNAc to Ser or Thr of the polypeptide backbone. They have in common the Gal(beta 1 leads to 3)GalNAc core unit, which bears one or more N-acetyllactosamine branches. The latter are terminated either by Fuc in (alpha 1 leads to 2) linkage or by GlcNAc in (alpha 1 leads to 4) linkage to Gal. Both terminal sequences are considered to be porcine blood-group H antigenic determinants. Employing 500-MHz 1H-NMR spectroscopy, the spectral features of the oligosaccharide-alditols corresponding to these chains were established. Insight could be gained into the microheterogeneity displayed by some of the alditol fractions as to the distribution of the terminating Fuc and GlcNAc residues over the various branches. Such information can hardly be obtained using other approaches.

Primary-structure determination of fourteen neutral oligosaccharides derived from bronchial-mucus glycoproteins of patients suffering from cystic fibrosis, employing 500-MHz 1H-NMR spectroscopy

The structure of carbohydrate units of bronchial-mucus glycoproteins obtained from cystic fibrosis patients was investigated by 500-MHz 1H-NMR spectroscopy and methylation analysis. To that purpose, the mucin was subjected to alkaline borohydride degradation. Neutral oligosaccharide-alditols, ranging in size from disaccharides to pentasaccharides, were isolated. Eight compounds could be purified to homogeneity; furthermore, three fractions were obtained consisting mainly of two components. For all 14 compounds the primary structure could be elucidated. 500-MHz 1H-NMR spectroscopy was found to be effective in detecting heterogeneity and to be invaluable for the determination of structures in mixtures of oligosaccharide-alditols. The structures can be divided into two groups depending on the core disaccharide. One group contains Gal(beta 1 leads to 3)GalNAc-ol as common structural element, the other GlcNAc(beta 1 leads to 3)GalNAc-ol. Both disaccharides were identified as such; the other compounds can be conceived as extensions thereof. The most complex representatives of the two groups are: (formula; see text) The italicized structural elements, comprising the SSEA-1 determinant and the type-1 blood-group-H determinant, are novel sequences in oligosaccharide chains of mucin-type glycoproteins.