Primary structure of a low-molecular-mass N-linked oligosaccharide from hemocyanin of Lymnaea stagnalis. 3-O-methyl-D-mannose as a constituent of the xylose-containing core structure in an animal glycoprotein

Hemocyanin from the freshwater snail Lymnaea stagnalis is a high-molecular-mass copper-containing oxygen-transport protein, which occurs freely dissolved in the hemolymph. It is a glycoprotein containing fucose, xylose, 3-O-methylmannose, 3-O-methylgalactose, mannose, galactose, N-acetylgalactosamine and N-acetylglucosamine residues as sugar constituents. The N-glycosidic carbohydrate chains of this glycoprotein were released by hydrazinolysis of a pronase digest and subsequently fractionated as oligosaccharide-alditols on Bio-Gel P-4 followed by Lichrosorb-NH2. Investigation with 500-MHz 1H-NMR spectroscopy, in conjunction with sugar and methylation analysis revealed the lowest-molecular-mass glycan chain to have the structure: (Formula: see text).     

Characterization of N-linked gluco-oligomannose type of carbohydrate chains of glycoproteins from the ovary of the starfish Asterias rubens (L.)

Glycoproteins were isolated from the ovary of the starfish Asterias rubens (L.). After delipidation, sugar analysis revealed the presence of mannose, glucose and N-acetylglucosamine in a molar ratio of 9.0:1.3:2.3. Subsequently, hydrazinolysis, re-N-acetylation, reduction and high-voltage paper electrophoresis were carried out, resulting in a mixture of neutral oligosaccharide alditols which was fractionated on Bio-Gel P-4. The alditols, investigated by 500-MHz 1H-NMR spectroscopy, turned out to be of the oligomannose type or of the gluco-oligomannose type containing 9 mannose and 1-3 glucose residues. The most abundant compounds were established to be: (Formula: see text) and (Formula: see text).     

Structures of oligomannoside chains of alpha-mannosidase from porcine kidney

Lysosomal acid alpha-mannosidase from porcine kidney was found to contain mannose (4.8%), galactose (0.9%), fucose (0.5%), N-acetylglucosamine (3.1%), and mannose 6-phosphate (0.1%). Approximately 50% of the total hexose of the oligosaccharide chains could be released by endo-beta-N-acetylglucosaminidase-H (endo-H). They were predominantly neutral, oligomannoside-type oligosaccharides containing 5, 6, and 9 mannose residues, respectively, in the centesimal ratio of 36:25:34. 500-MHz 1H-NMR spectroscopy in conjunction with sequential exoglycosidase digestion of the reduced compounds revealed that each of the three fractions consisted of a single isomer only; the Man9 compound has the following structure: (Formula: see tex). The Man6-compound lacks Man residues D1, D2, and D3, while the Man5-compound lacks Man-C as well. In addition to the neutral ones, some (5%) phosphorylated oligomannoside-type oligosaccharides were obtained. The endo-H resistant glycopeptides were subjected to hydrazinolysis. Approximately 60% of the oligosaccharides released by hydrazine were found to be of rather small size; their composition can be represented asMan2-3GlcNAc[Fuc]0-1GlcNAcol. The remaining 40% consist of larger-size galactose-containing, N-acetyllactosamine-type oligosaccharides. Studies involving sequential exoglycosidase digestion and 500-MHz 1H-NMR spectroscopy performed on the highly purified small-sized compounds revealed the following four structures for the endo-H-resistant oligosaccharides: (Formula: see text).     

Structure determination of two oligomannoside-type glycopeptides obtained from bovine lactotransferrin,by 500 MHz 1H-NMR spectroscopy

The elucidation of the structures of two carbohydrates units, N-glycosidically linked to an asparagine residue of bovine lactotransferrin, is described. These carbohydrate structures are of the oligomannoside type and contain eight or nine mannose residues, respectively. The potency of 500 MHz ¹H-NMR spectroscopy in primary structure determination of two closely related carbohydrate chains present in a mixture is demonstrated. This implies that 500 MHz ¹H-NMR spectroscopy can disclose microheterogeneity which is almost untraceable using other approaches.     

Structures of the sugar chains of interferon-gamma produced by human myelomonocyte cell line HBL-38

Interferon-gamma produced by the human myelomonocyte cell line HBL-38 contained galactose, mannose, fucose, N-acetylglucosamine, and N-acetylneuraminic acid as sugar components. Sugar chains were liberated from interferon-gamma by hydrazinolysis. Free amino groups of the sugar chains were acetylated and the reducing-end sugar residues were tagged with 2-aminopyridine under new reaction conditions in which no sialic acid residue was hydrolyzed. The pyridylamino (PA-) derivatives of the sugar chains thus obtained were purified by gel filtration and reversed-phase HPLC. Seven major PA-sugar chains were isolated and the structure of each purified PA-sugar chain was identified by stepwise exoglycosidase digestion and 500-mHz 1H-NMR spectroscopy. The results indicated that the structures of the major PA-sugar chains were of the biantennary type, to which 0 to 2 mol of fucose and 1 to 2 mol of N-acetylneuraminic acid were linked as shown below. (formula; see text)     

Structural studies of the carbohydrate chains of human gamma-interferon

Human gamma-interferon (IFN-gamma) was prepared biotechnologically using Chinese hamster ovary cells. These cells were shown to be able to produce glycosylated IFN-gamma. Sugar analysis revealed the presence of Man, Gal, GlcNAc, NeuAc and Fuc residues in a molar ratio of 3.8:2.0:3.5:0.6:0.4 suggesting the occurrence of N-glycosidically linked N-acetyllactosamine type of carbohydrate chains. For structure determination of these chains, the glycoprotein was subjected to the hydrazinolysis procedure, yielding oligosaccharide-alditols. The latter compounds were analysed by 500-MHz 1H-NMR spectroscopy. The carbohydrate material was found to consist of biantennary structures, exhibiting microheterogeneity as to the terminal sialic acids and the core Fuc residue: (Formula: see text). As similar carbohydrates are present on several human secreted proteins, this glycosyl group is not expected to be immunogenic in man. It remains to be established to what extent the carbohydrate chains of this biotechnologically produced IFN-gamma are identical to those of naturally occurring human IFN-gamma.     

Structural studies on the O-glycosidically linked carbohydrate chains of glucoamylase G1 from Aspergillus niger

Glucoamylase G1 from Aspergillus niger contains an unusual type of carbohydrate-protein linkage, involving mannose O-glycosidically linked to serine and threonine. The majority of the neutral oligosaccharides of glucoamylase G1 are located in a region of about 70 amino acid residues which carries about 35 oligosaccharide units [(1983) Carlsberg Res. Commun. 48, 517-527]. Structural analysis was performed on the O-linked carbohydrates of a tryptic fragment from glucoamylase G1 comprising the segment characterized by a high degree of glycosylation. The carbohydrate structures released by trifluoroacetolysis were elucidated using sugar analysis, methylation analysis, mass spectrometry, chromium trioxide oxidation, digestion with alpha-mannosidase and 1H-NMR spectroscopy. The following structures could be identified. (formula; see text)     

The structure of the carbohydrate units of the carboxyl-terminal peptide of procollagen as elucidated by 500 MHz 1H-NMR spectroscopy

The oligosaccharides of chick embryo type I procollagen were isolated from the carboxyl-terminal propeptide fragment by exhaustive digestion with papain and pronase, and then purified as a mixture of glycopeptides. The structures of the oligosaccharides were established by high-resolution ¹H-NMR spectroscopy and found to be a mixture with respect to the non-reducing terminal residues as shown below:

The percentages refer to the relative amount of those mannose residues present in the mixture. The data suggest that the oligosaccharides are a microheterogeneous mixture of high-mannose type glycans containing between six and nine mannose residues per carbohydrate unit. Such carbohydrate chains, although not uncommon for glycoproteins, had never been found before for collagen or collagen-related compounds.     

Determination of the structure of the carbohydrate chains of acid alpha-glucosidase from human placenta

Acid alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) from human placenta (70 and 76 kDa) was found to contain 4 N-glycosidic carbohydrate chains per molecule. Sugar analysis of purified enzyme revealed the presence of mannose, N-acetylglucosamine and fucose at a molar ratio of 5.0:2.0:0.6. In addition, trace amounts of galactose and N-acetylneuraminic acid were detected. The sugar chains were liberated from the polypeptides by the hydrazinolysis procedure and subsequently fractionated by gel filtration and HPLC. Purified compounds were investigated by 500-MHz 1H-NMR spectroscopy. Oligomannoside-type chains of intermediate size, e.g., Man5GlcNAcGlcNAc-ol and Man7GlcNAcGlcNAc-ol, and N-type chains of smaller size e.g., Man2-3GlcNAc[Fuc]0-1GlcNAc-ol, were demonstrated to be present at a ratio of 2:3. In addition, a small amount of sialylated N-acetyllactosamine-type chains has been found. The possible biosynthetic route of the fucose-containing small-size chains is discussed.     

Structures of sugar chains of a p-nitrophenyl acetate-hydrolyzing esterase from the microsomes of rat liver

The structures of sugar chains of a p-nitrophenyl acetate-hydrolyzing esterase from the microsomes of rat liver were established. The enzyme contained mannose and glucosamine as sugar components. Asparagine-linked sugar chains of the esterase were liberated by hydrazinolysis. After N-acetylation of the hydrazinolysate, the reducing ends of the sugar chains were coupled with 2-aminopyridine. Fluorescent pyridylamino (PA-) derivatives of sugar chains thus obtained were purified by gel filtration and reversed-phase HPLC. Eleven PA-sugar chains were obtained. The structures of the PA-sugar chains were first identified by HPLC using two series of separation systems by which 11 PA-oligomannose-type sugar chains with known structures could be separated. Further elucidation of the structures of each PA-sugar chain was performed by exoglycosidase digestions and partial acetolysis. The structures of two of the PA-sugar chains were further confirmed by 500 mHz 1H-NMR spectroscopy.     

Primary structure determination of seven novel N-linked carbohydrate chains derived from hemocyanin of Lymnaea stagnalis. 3-O-methyl-D-galactose and N-acetyl-D-galactosamine as constituents of xylose-containing N-linked oligosaccharides in an animal glycoprotein

Hemocyanin from the freshwater snail Lymnaea stagnalis is a high-molecular-mass copper-containing glyco-protein which functions as oxygen carrier in the hemolymph. To release the carbohydrate chains, the protein was digested by pronase followed by hydrazinolysis and reduction. The oligosaccharide-alditols were purified by gel permeation chromatography on Bio-Gel P-4, followed by HPLC on a Lichrosorb-NH2 column. Using 500-MHz 1H-NMR spectroscopy, in conjunction with sugar, methylation and deamination analysis, the following seven novel primary oligosaccharide structures could be unravelled. (Formula: see text).     

Primary structure of the low-molecular-weight carbohydrate chains of Helix pomatia alpha-hemocyanin. Xylose as a constituent of N-linked oligosaccharides in an animal glycoprotein

alpha-Hemocyanin of Helix pomatia is a copper-containing glycoprotein which serves as an oxygen carrier in the hemolymph. Its carbohydrate moiety has as constituents fucose, xylose, 3-O-methylgalactose, mannose, galactose, N-acetylgalactosamine, and N-acetyl-glucosamine residues. Alkaline borhydride did not split off any carbohydrate material, suggesting the absence of O-glycosidic chains. The N-glycosidic carbohydrate chains of this glycoprotein were liberated by hydrazinolysis of a Pronase digest then fractionated as alditols on Bio-Gel P-4. The fractions containing the low-molecular-weight glycans were investigated by 500-MHz 1H NMR spectroscopy in conjunction with sugar and methylation analysis. The largest, and most abundant, compound was established to be: (Formula: see text). Another compound was characterized as the afuco analogue of this structure. H. pomatia alpha-hemocyanin is the first example of an animal glycoprotein having xylose as a constituent of N-glycosidic carbohydrate chains.     

Possible pathway for the processing of sugar chains containing xylose in plant glycoproteins deduced on structural analyses of sugar chains from Ricinus communis lectins

The structures of sugar chains from two lectins in seeds of the castor bean (Ricinus communis) were identified. The sugar chains were liberated from the lectins by hydrazinolysis. After N-acetylation, the reducing-end residues of the sugar chains were coupled with 2-aminopyridine. The pyridylamino derivatives thus obtained were purified by gel filtration and HPLC. The structures of the purified derivatives were identified by component sugar analysis, stepwise exoglycosidase digestion, partial acetolysis, and 500 MHz 1H-NMR spectroscopy. A new processing pathway for sugar chains in plant glycoproteins was proposed on the basis of the structures of the sugar chains.     

A new sugar chain of the proteinase inhibitor from latex of Carica papaya

The structure of a sugar chain of the proteinase inhibitor from the latex of Carica papaya was studied. Sugar chains liberated on hydrazinolysis were N-acetylated, and their reducing-end residues were tagged with 2-aminopyridine. One major sugar chain was detected on size-fractionation and reversed-phase HPLC analyses. The structure of the PA-sugar chain was determined by two-dimensional sugar mapping combined with sequential exoglycosidase digestion and partial acid hydrolysis, and by 750 MHz 1H-NMR spectroscopy. The structure found was Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3) (Xylbeta1-2)Manbeta1- 4GlcNAcbeta1-4(Fucalpha1-3)GlcNAc. This sugar chain represents a new plant-type sugar chain with five mannose residues.     

Structure of a sugar chain of a protease inhibitor isolated from barbados pride (Caesalpinia pulcherrima Sw.) seeds

An asparagine-linked sugar chain of a protease inhibitor from barbados pride (Caesalpinia pulcherrima Sw.) was liberated by hydrazinolysis. After N-acetylation, the reducing end residue of this carbohydrate unit was coupled with 2-aminopyridine and the pyridylamino (PA-) derivative was purified by gel-filtration and reversed-phase HPLC. The structure of the resulting PA-sugar chain was determined mainly by stepwise exoglycosidase digestions and 500 MHz 1H-NMR spectroscopy and proved to be as follows: (formula; see text).     

Structural analysis of the N-linked carbohydrate chains of the 55-kDa glycoprotein family (PZP3) from porcine zona pellucida.

The N-linked oligosaccharides, released by hydrazinolysis from the major 55-kDa family, PZP3, of porcine zona pellucida glycoproteins, were separated into neutral (28%) and acidic (72%) carbohydrate chains by anion-exchange HPLC. By competition assay, it was shown that the mixture of neutral chains has the sperm-receptor activity, while that of the acidic chains has no activity. Their carbohydrate structures were analyzed after the reducing ends were modified with 2-aminopyridine. The neutral chains were fractionated into several components by reverse-phase and normal-phase HPLC. By sequential glycosidase digestion and 500-MHz 1H-NMR spectroscopy, the structures of three major components were determined. The structures of some of the minor components were analyzed only by sequential glycosidase digestion. By these analyses, it was found that a diantennary complex-type structure with a fucose residue was predominant in the neutral chains. Furthermore, the analyses of the endo-beta-galactosidase digests of the acidic chains revealed that the partially sulfated and sialylated N-acetyllactosamines are linked to the non-reducing ends of diantennary, triantennary, and tetra-antennary complex-type neutral chains, forming heterogeneous acidic chains.     

Primary structure of a novel N-glycosidic carbohydrate unit, derived from hen ovomucoid. A 500-MHz 1H-NMR study

The N-glycosidic carbohydrate chains of hen beta-ovomucoid were released from the protein by hydrazinolysis, and separated by HPLC. Primary structural analysis of 3 major fractions was conducted by applying 500-MHz 1H-NMR spectroscopy in combination with methylation analysis. One of the fractions investigated appeared to consist of an intersected penta-antennary structure extended with one Gal residue. The location of the latter in a certain branch could be established unambiguously by NMR. This structure is a novel member of the family of N-glycosidic carbohydrates of glycoproteins.     

Structure determination of the major asparagine-linked sugar chain of human factor VIII--von Willebrand factor

N-glycosidically-linked glycans released by hydrazinolysis of human factor VIII/von Willebrand factor (FVIII/vWf) were separated by high-voltage electrophoresis. Five fractions were obtained, one of them representing 60% of the total amount of the N-glycosidically-linked glycans of FVIII/vWf. On the basis of the carbohydrate composition, methylation analysis and 500 MHz 1H-NMR spectroscopy, we describe the primary structure of this major glycan which is of the monosialylated and monofucosylated biantennary N-acetyllactosaminic type.     

Structural analysis of the carbohydrate chains of beta-N-acetylhexosaminidases from bovine brain.

The oligosaccharide structures of bovine brain beta-N-acetylhexosaminidases A and B (EC 3.2.1.30) were studied at the glycopeptide level by employing 500 MHz 1H-n.m.r. spectroscopy and methylation analysis involving g.l.c.-m.s. More than 90% of the chains were found to be of the oligomannoside type, containing, on average, five to six mannose residues. Biantennary N-acetyl-lactosamine-type chains terminated in N-acetylneuraminic acid were found to comprise the remaining 5-10% of the total carbohydrate. The isoenzyme forms A and B do not differ from each other in the structure of their carbohydrate moiety, but do deviate in carbohydrate content and, in consequence, in the number of carbohydrate chains per molecule.     

Major carbohydrate structures at five glycosylation sites on murine IgM determined by high resolution 1H-NMR spectroscopy

Mouse myeloma immunoglobulin IgM heavy chains were cleaved with cyanogen bromide into nine peptide fragments, four of which contain asparagine-linked glycosylation. Three glycopeptides contain a single site, including Asn 171, 402, and 563 in the intact heavy chain. Another glycopeptide contains two sites at Asn 332 and 364. The carbohydrate containing fragments were treated with Pronase and fractionated by elution through Bio-Gel P-6. The major glycopeptides from each site were analyzed by 500 MHz 1H-NMR and the carbohydrate compositions determined by gas-liquid chromatography. The oligosaccharide located at Asn 171 is a biantennary complex and is highly sialylated. The amount of sialic acid varies, and some oligosaccharides contain alpha 1,3-galactose linked to the terminal beta 1,4-galactose. The oligosaccharides at Asn 332, Asn 364, an Asn 402 are all triantennary and are nearly completely sialylated on two branches and partially sialylated on the triantennary branch linked beta 1,4 to the core mannose. The latter is sialylated about 40% of the time for all three glycosylation sites. The major oligosaccharide located at Asn 563 is of the high mannose type. The 1H-NMR determination of structures at Asn 563 suggests that the high mannose oligosaccharide contains only three mannose residues.