Use of Wisteria floribunda agglutinin affinity chromatography in the structural analysis of the bovine lactoferrin N-linked glycosylation

Background

Over the years, the N-glycosylation of both human and bovine lactoferrin (LF) has been studied extensively, however not all aspects have been studied in as much detail. Typically, the bovine LF complex-type N-glycans include certain epitopes, not found in human LF N-glycans, i.e. Gal(α1-3)Gal(β1-4)GlcNAc (αGal), GalNAc(β1-4)GlcNAc (LacdiNAc), and N-glycolylneuraminic acid (Neu5Gc). The combined presence of complex-type N-glycans, with αGal, LacdiNAc, LacNAc [Gal(β1-4)GlcNAc], Neu5Ac (N-acetylneuraminic acid), and Neu5Gc epitopes, and oligomannose-type N-glycans complicates the high-throughput analysis of such N-glycoprofiles highly.

Methods

For the structural analysis of enzymatically released N-glycan pools, containing both LacNAc and LacdiNAc epitopes, a prefractionation protocol based on Wisteria floribunda agglutinin affinity chromatography was developed. The sub pools were analysed by MALDI-TOF-MS and HPLC-FD profiling, including sequential exoglycosidase treatments.

Results

This protocol separates the N-glycan pool into three sub pools, with (1) free of LacdiNAc epitopes, (2) containing LacdiNAc epitopes, partially shielded by sialic acid, and (3) containing LacdiNAc epitopes, without shielding by sialic acid. Structural analysis by MALDI-TOF-MS and HPLC-FD showed a complex pattern of oligomannose-, hybrid-, and complex-type di-antennary structures, both with, and without LacdiNAc, αGal and sialic acid.

Conclusions

Applying the approach to bovine LF has led to a more detailed N-glycome pattern, including LacdiNAc, αGal, and Neu5Gc epitopes, than was shown in previous studies.

General significance

Bovine milk proteins contain glycosylation patterns that are absent in human milk proteins; particularly, the LacdiNAc epitope is abundant. Analysis of bovine milk serum proteins is therefore excessively complicated. The presented sub fractionation protocol allows a thorough analysis of the full scope of bovine milk protein glycosylation. This article is part of a Special Issue entitled Glycoproteomics.     

Sulfation of sialyl N-acetyllactosamine oligosaccharides and fetuin oligosaccharides by keratan sulfate Gal-6-sulfotransferase

We have previously cloned keratan sulfate Gal-6-sulfotransferase (KSGal6ST), which transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 6 of Gal residue of keratan sulfate. In this study, we examined whether KSGal6ST could transfer sulfate to sialyl N -acetyllactosamine oligosaccharides or fetuin oligo-saccharides. KSGal6ST expressed in COS-7 cells catalyzed transfer of sulfate to NeuAcalpha2-3Galbeta1-4GlcNAc (3'SLN), NeuAcalpha2-3Galbeta1-4GlcNAcbeta1-3Galbeta1-4Gl cNAc (SL1L1), NeuAcalpha2-3Galbeta1-4(6-sulfo)GlcNAcbeta1-3(6-sulfo) Galbeta1-4(6-su lfo)GlcNAc (SL2L4), and their desialylated derivatives except for Galbeta1-4GlcNAc, but not to NeuAcalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAc (SLex). When the sulfated product formed from 3'SLN was degraded with neuraminidase and reduced with NaBH(4), the resulting sulfated disaccharide alditol showed the same retention time in SAX-HPLC as that of [(3)H]Gal(6SO(4))beta1-4GlcNAc-ol. KSGal6ST also catalyzed sulfation of fetuin. When the sulfated oligosaccharides released from the sulfated fetuin after sequential digestion with proteinase and neuraminidase were subjected to a reaction sequence of hydrazin-olysis, deaminative cleavage and NaBH(4)reduction, the major product was co-eluted with [(3)H]Gal(6SO(4))beta1-4anhydromannitol in SAX-HPLC. These observations show that KSGal6ST is able to sulfate position 6 of Gal residue of 3'SLN and fetuin oligosaccharides. The relative rates of the sulfation of SL2L4 was much higher than the rate of the sulfation of keratan sulfate. These results suggest that KSGal6ST may function in the sulfation of sialyl N -acetyllactosamine oligosaccharide chains attached to glycoproteins.     

LacdiNAc- and LacNAc-containing glycans induce granulomas in an in vivo model for schistosome egg-induced hepatic granuloma formation

Schistosomes, major parasitic helminths, express numerous glycoconjugatesthat provoke humoral and cellular immune responses in the infectedhuman host. The main pathology in schistosomiasis is due tothe formation of granulomas around tissue-trapped eggs and theresulting organ damage. By using a mouse model of inductionof granulomas by hepatic implantation of antigen-coated beads,it has been determined that the glycan part of schistosomalsoluble egg antigens (SEA) initiates granulomogenesis. To identifywhich individual glycan elements in this complex SEA mixtureare granulomogenic, we have tested in the same mouse model conjugatesof various synthetic oligosaccharides characteristic for schistosomeeggs, including GalNAcß1-4GlcNAc (LacdiNAc, LDN),Galß1-4(Fuc1-3)GlcNAc (Lewis^x), Fuc1-2Fuc1-3GlcNAc(DF-Gn), and Fuc1-3GalNAcß1-4(Fuc1-3)GlcNAc (F-LDN-F).Ribonuclease (RNase) A and B, and different fetuin glycoformswere included as controls. Only beads that carry glycoconjugateswith terminal LacdiNAc or Galß1-4GlcNAc (LacNAc, LN)elements gave rise to granulomas, with macrophage, lymphocyte,and eosinophil levels similar to the granulomatous lesions causedby schistosome eggs in a natural infection. Uncoated beads,and beads coated with fucosylated glycoconjugates or glycoconjugateslacking terminally exposed Gal or GalNAc, only attracted a monolayerof macrophages. These results indicate that the formation ofhepatic granulomas is triggered specifically by glycoconjugateswhich carry terminal LacNAc or LacdiNAc, both constituents ofthe schistosome egg.     

Ovarian cancer alpha 1,3-L-fucosyltransferase. Differentiation of distinct catalytic species with the unique substrate, 3'-sulfo-N-acetyllactosamine in conjunction with other synthetic acceptors.

Several N-acetyllactosamine (LacNAc) derivatives were tested as acceptors for alpha 1,3-L-fucosyltransferase present in human ovarian cancer sera and ovarian tumor. The enzyme of the soluble fraction of tumor was purified to apparent homogeneity by chromatography on bovine IgG glycopeptide-Sepharose followed by Sephacryl S-200 (M(r) < 67,000). As compared with 2'-methyl LacNAc, 3'-sulfo LacNAc was about 5-fold more sensitive in measuring alpha 1,3-fucosyltransferase in sera (Km, 3'-sulfo LacNAc, 0.12 mM; 2'-methyl LacNAc, 6.67 mM). When ovarian cancer serum was the enzyme source, either the sulfate group or a sialyl moiety at C-3' of LacNAc enhanced the acceptor ability (341 and 242%, respectively), whereas the sulfate group at C-2' or C-6' reduced the activity (22-36%); sulfate at C-6 or fucose at C-2' increased the activity (172 and 253%). The beta-benzylation of the reducing end, in general, increased the activity 2-3-fold. The enzyme of the soluble fraction of tumor exhibited more activity toward 3'-sulfo LacNAc (447%), 2'-fucosyl-LacNAc (436%), and 6-sulfo LacNAc (272%). Very low activity was observed with 3'-sialyl LacNAc (12.4%), 2'-sulfo LacNAc (33%), and 6'-sulfo LacNAc (5%); Fuc alpha 1,2Gal beta 1,3GlcNAc beta-O-p-nitrophenyl (166%), 2-methyl Gal beta 1,3GlcNAc beta-O-benzyl (204%), and 3-sulfo Gal beta 1,3GlcNAc (415%) also acted as acceptors, indicating the coexistence of alpha 1,3- and alpha 1,4-fucosyltransferase. The tumor particulate enzyme behaved entirely different, exhibiting low activity with 3'-sulfo LacNAc (39%) and 2'-fucosyl-LacNAc (148%); 3'-sialyl, 6'-sulfo, 6-sulfo, or 2'-sulfo LacNAc were 3, 43, 53, and 10% active, respectively. Thus, the ovarian cancer serum alpha 1,3-fucosyltransferase acts equally well on H-type 2,3'-sialyl LacNAc and 3'-sulfo LacNAc, but not on H-type 1. The enzyme of soluble tumor fraction acts on H-type 2,3'-sulfo LacNAc as well as H-type 1 but poorly on 3'-sialyl LacNAc. The tumor particulate enzyme acts on H-type 2 but poorly on 3'-sulfo or 3'-sialyl LacNAc and is inactive with H-type 1. When normal serum was examined with synthetic acceptors, > 80% activity was found as alpha 1,2-fucosyltransferase and the rest as alpha 1,3-fucosyltransferase. A screening of 21 ovarian cancer and 3 normal sera (3'-sulfo LacNAc as acceptor) showed 17-572% increase (average increase, 188%) of alpha 1,3-fucosyltransferase activity in cancer.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cell surface n-acetylneuraminic acid alpha2,3-galactoside-dependent intercellular adhesion of human colon cancer cells

Sialoglycans on the cell surface of human colon cancer (HCC) cells have been implicated in cellular adhesion and metastasis. To clarify the role of N-acetylneuraminic acid (NeuAc) linked alpha2,3 to galactose (Gal) on the surface of HCC cells, we studied the intercellular adhesion of HCC cell lines expressing increasing NeuAcalpha2,3Gal-R. Our model system consisted of the HCC SW48 cell line, which inherently possesses low levels of cell surface alpha2,3 and alpha2,6 sialoglycans. To generate SW48 clonal variants with elevated cell surface NeuAcalpha2,3Gal-R linkages, we transfected the expression vector, pcDNA3, containing either rat liver cDNA encoding Galbeta1,3(4)GlcNAc alpha2,3 sialyltransferase (ST3Gal III) or human placental cDNA encoding Galbeta1,3GalNAc/Galbeta1,4GlcNAc alpha2,3 sialyltransferase (ST3Gal IV) into SW48 cells. Selection of neomycin-resistant clones (600 microgram G418/ml) having a higher percentage of cells expressing NeuAcalpha2,3Gal-R (up to 85% positive Maackia amurenis agglutinin staining compared with 30% for wild type cells) was performed. These ST3Gal III and ST3Gal IV clonal variants demonstrated increased adherence to IL-1beta-activated human umbilical vein endothelial cells (HUVEC) (up to 90% adherent cells compared with 63% for wild type cells). Interestingly, ST3Gal III and ST3Gal IV clonal variants also bound non-activated HUVEC up to 4-fold more effectively than wild type cells. Cell surface NeuAcalpha2,3Gal-R expression within the various SW48 clonal variants correlated directly with increased adhesion to HUVEC (r=0.84). Using HCC HT-29 cells, which express high levels of surface NeuAcalpha2,3Gal-R, addition of synthetic sialyl, sulfo or GalNAc Lewis X structures were found to specifically inhibit intercellular adhesion. At 1.0mM, NeuAcalpha2,3Galbeta1,3(Fucalpha1, 4)GlcNAc-OH and Galbeta1,4(Fucalpha1,3)GlcNAcbeta1,6(SE-6Galbeta1++ +, 3)GalNAcalpha1-O-methyl inhibited HT-29 cell adhesion to IL-1beta-stimulated HUVEC by 100% and 68%, respectively. GalNAcbeta1, 4(Fucalpha1,3)GlcNAcbeta1-O-methyl and GalNAcbeta1,4(Fucalpha1, 3)GlcNAcbeta1,6Manalpha1,6Manbeta1-0-C30H61, however, did not possess inhibitory activity. In conclusion, these studies demonstrated that cell surface NeuAcalpha2,3Gal-R expression is involved in HCC cellular adhesion to HUVEC. These specific carbohydrate-mediated intercellular adhesive events may play an important role in tumor angiogenesis, metastasis and growth control.     

Characterization of the N-linked oligosaccharides of megalin (gp330) from rat kidney

Megalin (gp 330) is a large cell surface receptor expressed on the apical surfaces of epithelial tissues, that mediates the binding and internalization of a number of structurally and functionally distinct ligands. In this paper we report the first detailed structural characterization of megalin-derived oligosaccharides. Using strategies based on mass spectrometric analysis, we have defined the structures of the N-glycans of megalin. The results reveal that megalin glycoprotein is heterogeneously glycosylated. The major N-glycans identified belong to the following two classes: high mannose structures and complex type structures, with complex structures being more abundant than high mannose structures. The major nonreducing epitopes in the complex-type glycans are: GlcNAc, Galbeta1-4GlcNAc (LacNAc), NeuAcalpha2-6Galbeta1-4GlcNAc (sialylated LacNAc), GalNAcbeta1-4[NeuAcalpha2-3]Galbeta1-4GlcNAc (Sd(a)) and Galalpha1-3Galbeta1-4GlcNAc. Most complex structures are characterized by the presence of (alpha1,6)-core fucosylation and the presence of a bisecting GlcNAc residue.     

Comparison of the enzymatic properties of mouse beta-galactoside alpha2,6-sialyltransferases,ST6Gal I and II

The cDNA encoding a second type of mouse beta-galactoside alpha2,6-sialyltransferase (ST6Gal II) was cloned and characterized. The sequence of mouse ST6Gal II encoded a protein of 524 amino acids and showed 77.1% amino acid sequence identity with human ST6Gal II. Recombinant ST6Gal II exhibited alpha2,6-sialyltransferase activity toward oligosaccharides that have the Galbeta1,4GlcNAc sequence at the nonreducing end of their carbohydrate groups, but it exhibited relatively low and no activity toward some glycoproteins and glycolipids, respectively. On the other hand, ST6Gal I, which has been known as the sole member of the ST6Gal-family for more than ten years, exhibited broad substrate specificity toward oligosaccharides, glycoproteins, and a glycolipid, paragloboside. The ST6Gal II gene was mainly expressed in brain and embryo, whereas the ST6Gal I gene was ubiquitously expressed, and its expression levels were higher than those of the ST6Gal II gene. The ST6Gal II gene is located on chromosome 17 and spans over 70 kb of mouse genomic DNA consisting of at least 6 exons. The ST6Gal II gene has a similar genomic structure to the ST6Gal I gene. In this paper, we have shown that ST6Gal II is a counterpart of ST6Gal I.     

The carbohydrate of bovine prothrombin. Occurrence of Gal beta 1 leads to 3GlcNAc grouping in asparagine-linked sugar chains.

Bovine prothrombin contains three asparagine-linked sugar chains in 1 molecule. The sugar chains were quantitatively released from the polypeptide backbone by hydrazinolysis. All of the oligosaccharides thus obtained contain N-acetylneuraminic acid. Sialidase treatment of these acidic oligosaccharides released three isomeric oligosaccharides, N-1, N-2 and N-3. N-3 was a typical complex type asparagine-linked sugar chain widely found in other glycoprotein, while N-1 and N-2 were unique, because they contain Gal beta 1 leads to 3GlcNAc grouping in the outer chain moiety. By comparing the data of methylation analysis of the acidic oligosaccharides before and after sialidase treatment, the structures of the sugar chains of bovine prothrombin were confirmed as a mixture of NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc leads to Asn, NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6[NeuAc alpha 2 leads to 3Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GlcNAc beta 1 leads to 2Man alpha 1 leads to 3]Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc leads to Asn, NeuAc alpha 2 leads to 3Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GlcNAc beta 1 leads to 2Man alpha 1 leads to 6[NeuAc alpha 2 leads to 3Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GlcNAc beta 1 leads to 2Man alpha 1 leads to 3]Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc leads to Asn and their partially desialized forms.     

Mucin biosynthesis revisited. The enzymatic transfer of Gal in beta 1,3 linkage to the GalNAc moiety of the core structure R1-GlcNAc beta 1,6GalNAc alpha-O-R2.

Synthetic glycosides containing the core, -Glc-NAc beta 1,6GalNAc alpha-, acted as acceptors for beta-galactosyltransferase of human ovarian tumor. A significant amount of Gal was transferred from UDP-Gal (100 nmol) to the alpha-benzylglycoside of LacNAc beta 1,6GalNAc (LGBn) (25.1 nmol of Gal) and the alpha-ortho-nitrophenylglycosides of LacNAc beta 1,6GalNAc (22.0 nmol of Gal), GlcNAc beta 1,6GalNAc (15.5 nmol of Gal), and Fuc alpha 1,3GlcNAc beta 1,6GalNAc (25.9 nmol of Gal); LacNAc beta 1,6(Gal beta 1,3)GalNAc alpha-O-Bn (where Bn is benzyl) was almost inactive (only 1.2 nmol of Gal), indicating the Gal transfer to the alpha-GalNAc moiety. The product from LGBn was isolated in microgram quantities and identified by fast atom bombardment mass spectrometry as LacNAc beta 1,6(Gal beta 1,3)GalNAc alpha-O-Bn. The alpha GalNAc:beta 1,3Gal transferase was present in high concentration in ovarian tumor tissue (ovarian cancer serum----1.4; ascitic fluid----0.9; tumor----17.4). Asialo Cowper's gland mucin (ACGM) at 5 mg/ml reaction mixture inhibited the transfer of Gal to LGBn (25.2 and 53.4% respectively for 2 and 18 h incubation at 37 degrees C); inhibition by LGBn was 13.4 and 24.5%, respectively. In contrast to the inhibition by ACGM (25.2-31.6%), there was substantial increase (13.4-35.7%) in the inhibition by LGBn, when the incubation for 2 h at 37 degrees C was continued for 40 h at 4 degrees C, indicating the high affinity of LGBn for the enzyme at lower temp. Km for LGBn in presence of ACGM was 7.6 mM and in absence, 2.7 mM; Km for ACGM (M(r) 200,000) in presence of LGBn was 16.1 microM and Ki for ACGM (as the inhibitor) was 41.7 microM. In comparison with two normal ovarian tissues, the enzyme was found to be low (55-67%) in three ovarian tumors and high (146-260%) in two ovarian and one uterus tumors, as measured with ACGM; the synthetic acceptors showed similar activities. The enzyme had nearly the same extent of activity in the pH range 6-8. Fuc alpha 1,3GlcNAc beta 1,6GalNAc alpha-O-ONP had the highest affinity for the enzyme. The present study demonstrates the feasibility of beta 1,3Gal attachment on alpha GalNAc, which has already been substituted by beta 1,6GlcNAc, then elongated by beta 1,4Gal and also terminated by alpha 1,3Fuc.     

Probing the substrate specificity of four different sialyltransferases using synthetic beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->O) (CH(2))7CH3 analogues general activating effect of replacing N-acetylglucosamine by N-propionylglucosamine

The acceptor specificities of ST3Gal III, ST3Gal IV, ST6Gal I and ST6Gal II were investigated using a panel of beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->O)(CH(2))(7)CH(3) analogues. Modifications introduced at either C2, C3, C4, C5, or C6 of terminal D-Gal, as well as N-propionylation instead of N-acetylation of subterminal D-GlcN were tested for their influence on the alpha-2,3- and alpha-2,6-sialyltransferase acceptor activities. Both ST3Gal enzymes displayed the same narrow acceptor specificity, and only accept reduction of the Gal C2 hydroxyl function. The ST6Gal enzymes, however, do not have the same acceptor specificity. ST6Gal II seems less tolerant towards modifications at Gal C3 and C4 than ST6Gal I, and prefers beta-D-GalpNAc-(1-->4)-beta-D-GlcpNAc (LacdiNAc) as an acceptor substrate, as shown by replacing the Gal C2 hydroxyl group with an N-acetyl function. Finally, a particularly striking feature of all tested sialyltransferases is the activating effect of replacing the N-acetyl function of subterminal GlcNAc by an N-propionyl function.     

Antibodies against sialyloligosaccharides coupled to protein

The beta-(p-aminophenyl)ethylamine derivatives of sialyloligosaccharides can be coupled to proteins via their phenylisothiocyanate intermediates under conditions that preserve labile sugar linkages. Bovine serum albumin containing 10 to 40 mol of oligosaccharides/mol of protein and keyhole limpet hemocyanin containing 1,100 mol of oligosaccharide/mol of protein have been prepared with the following oligosaccharides: Neu-NAc alpha 2-3Gal beta 1-4Glc, NeuNAc alpha 2-6Gal beta 1-4Glc, Neu-NAc alpha 2-6Gal beta 1-4GlcNAc beta 1-4Glc, Gal beta 1-3[Neu-NAc alpha 2-6]GlcNAc beta 1-4Glc, and NeuNAc alpha 2-3Gal- beta 1-3[NeuNAc alpha 2-6]GlcNAc beta 1-4Glc. Rabbits immunized with these synthetic glycoproteins produce antibodies directed against the oligosaccharides. The specificities of these antibodies are determined by comparing inhibitory activities of structurally related oligosaccharides in radioimmunoassay and by double diffusion analysis in agarose gels using oligosaccharide-protein conjugates as precipitating antigens. The antibodies distinguish positional isomers of sialic acid.     

Identification and functional expression of a second human beta-galactoside alpha2,6-sialyltransferase, ST6Gal II.

BLAST analysis of the human and mouse genome sequence databases using the sequence of the human CMP-sialic acid:beta-galactoside alpha-2,6-sialyltransferase cDNA (hST6Gal I, EC2.4.99.1) as a probe allowed us to identify a putative sialyltransferase gene on chromosome 2. The sequence of the corresponding cDNA was also found as an expressed sequence tag of human brain. This gene contained a 1590 bp open reading frame divided in five exons and the deduced amino-acid sequence didn't correspond to any sialyltransferase already known in other species. Multiple sequence alignment and subsequent phylogenic analysis showed that this new enzyme belonged to the ST6Gal subfamily and shared 48% identity with hST6Gal-I. Consequently, we named this new sialyltransferase ST6Gal II. A construction in pFlag vector transfected in COS-7 cells gave raise to a soluble active form of ST6Gal II. Enzymatic assays indicate that the best acceptor substrate of ST6Gal II was the free disaccharide Galbeta1-4GlcNAc structure whereas ST6Gal I preferred Galbeta1-4GlcNAc-R disaccharide sequence linked to a protein. The alpha2,6-linkage was confirmed by the increase of Sambucus nigra agglutinin-lectin binding to the cell surface of CHO transfected with the cDNA encoding ST6Gal II and by specific sialidases treatment. In addition, the ST6Gal II gene showed a very tissue specific pattern of expression because it was found essentially in brain whereas ST6Gal I gene is ubiquitously expressed.     

Primary structure of the glycan chains of normal C 1 esterase inhibitor (C 1-INH) after NMR analysis at 400 MHz

The primary structural analysis of O- and N-linked carbohydrate chains of the C-1-esterase inhibitor purified from normal serum was carried out by 400-MHz 1H-NMR spectroscopy. C-1-esterase inhibitor protein of a molecular weight of 116,000 daltons contains 24 O-glycans: NeuAc (alpha 2-3) Gal (beta 1-3) GalNAc, 4 N-glycans: NeuAc (alpha 2-6) Gal (beta 1-4) (GlcNAc (beta 1-2) Man (alpha 1-3) [NeuAc (alpha 2-6) Gal (beta 1-4) GlcNAc (beta 1-2) Man (alpha 1-6)] Man (beta 1-4) GlcNAc (beta 1-4) GlcNAc and 2 N-glycans: NeuAc (alpha 2-3) Gal (beta 1-4) GlcNAc (beta 1-2) Man (alpha 1-3) [NeuAc (alpha 2-3) Gal (beta 1-4) GlcNAc (beta 1-2) Man (alpha 1-6)] Man (beta 1-4) GlcNAc (beta 1-4) GlcNAc. 30% of the N-glycans are fucosylated.     

alpha 2,3-Sialylation of terminal GalNAc beta 1-3Gal determinants by ST3Gal II reveals the multifunctionality of the enzyme. The resulting Neu5Ac alpha 2-3GalNAc linkage is resistant to sialidases from Newcastle disease virus and Streptococcus pneumoniae

Enzymatic alpha 2,3-sialylation of GalNAc has not been described previously, although some glycoconjugates containing alpha 2,3-sialylated GalNAc residues have been reported. In the present experiments, recombinant soluble alpha 2,3-sialyltransferase ST3Gal II efficiently sialylated the X(2) pentasaccharide GalNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc, globo-N-tetraose GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc, and the disaccharide GalNAc beta 1-3Gal in vitro. The purified products were identified as Neu5Ac alpha 2-3GalNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc, Neu5Ac alpha 2-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc, and Neu5Ac alpha 2-3GalNAc beta 1-3Gal, respectively, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, enzymatic degradations, and one- and two-dimensional NMR-spectroscopy. In particular, the presence of the Neu5Ac alpha 2-3GalNAc linkage was firmly established in all three products by a long range correlation between Neu5Ac C2 and GalNAc H3 in heteronuclear multiple bond correlation spectra. Collectively, the data describe the first successful sialyltransfer reactions to the 3-position of GalNAc in any acceptor. Previously, ST3Gal II has been shown to transfer to the Gal beta 1-3GalNAc determinant. Consequently, the present data show that the enzyme is multifunctional, and could be renamed ST3Gal(NAc) II. In contrast to ST3Gal II, ST3Gal III did not transfer to the X(2) pentasaccharide. The Neu5Ac alpha 2-3GalNAc linkage of sialyl X(2) was cleaved by sialidases from Arthrobacter ureafaciens and Clostridium perfringens, but resisted the action of sialidases from Newcastle disease virus and Streptococcus pneumoniae. Therefore, the latter two enzymes cannot be used to differentiate between Neu5Ac alpha 2-3GalNAc and Neu5Ac alpha 2-6GalNAc linkages, as has been assumed previously.     

Structural characterization of oligosaccharides in the milk of an African elephant (Loxodonta africana africana)

The oligosaccharides present in the milk of an African elephant (Loxodonta africana africana), collected 4 days post partum, were separated by size exclusion-, anion exchange- and high-performance liquid chromatography (HPLC) before characterisation by (1)H NMR spectroscopy. Neutral and acidic oligosaccharides were identified. Neutral oligosaccharides characterised were isoglobotriose, Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc, Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc, Gal(alpha1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc and a novel oligosaccharide that has not been reported in the milk or colostrum of any other mammal: Gal(alpha1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc. Acidic oligosaccharides that are also found in the milk of Asian elephant were Neu5Ac(alpha2-3)Gal(beta1-4)Glc, Neu5Ac(alpha2-6)Gal(beta1-4)Glc, Neu5Ac(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]Glc, Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc, Neu5Ac(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc, Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc and Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3){Gal(alpha1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-6)}Gal(beta1-4)Glc, while Neu5Gc(alpha2-3)Gal(beta1-4)Glc, Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)[Fuc(alpha1-3)]Glc, Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)[Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc and Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3){Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-6)}Gal(beta1-4)Glc have not been found in Asian elephant milk. The oligosaccharides characterised contained both alpha(2-3)- and alpha(2-6)-linked Neu5Ac residues. They also contain only the type II chain, as found in most non-human, eutherian mammals.     

The sugar chains of cold-insoluble globulin. A protein related to fibronectin.

Cold-insoluble globulin isolated from bovine plasma contains six asparagine-linked sugar chains in 1 molecule (a dimeric form). These sugar chains were released from the polypeptide backbone by hydrazinolysis and labeled by reduction with NaB[3H]4. Most of these sugar chains contain N-acetylneuraminic acid and can be separated by paper electrophoresis. By combination of sequential exoglycosidase digestion and methylation study, their structures were elucidated as Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc, NeuAc alpha 2 leads to 6 or 4Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 4 or 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc, NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6[NeuAc alpha 2 4Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GlcNAc beta 1 leads to 2Man alpha 1 leads to 3]-Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc and NeuAc alpha 2 leads to 4Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GlcNAc beta 1 leads to 2Man alpha 1 leads to 6[NeuAc alpha 2 leads to 4Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GlcNAc beta 1 leads to 2Man alpha 1 leads to 3]man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc.     

Neutral oligosaccharides of bovine submaxillary mucin. A combined mass spectrometry and 1H-NMR study.

Twenty-two neutral O-linked oligosaccharides ranging from monosaccharides to octasaccharides were identified in bovine submaxillary-gland-mucin glycoprotein by a combination of liquid secondary-ion mass spectrometry, methylation analysis and 1H-NMR. Only five of these have been previously detected in bovine submaxillary-gland mucin although several have been described from other sources of mucin. The structures include short linear sequences 3-linked to N-acetylgalactosaminitol (GalNAcol) and branched structures based on either a GlcNAc(beta 1-6) [Gal(beta 1-3)]GalNAcol or GlcNAc(beta 1-6)[GlcNAc(beta 1-3)]GalNAcol core region. Oligosaccharides not previously characterised from any source were the disaccharide GalNAc alpha 1-6GalNAcol (GalNAc, N-acetylgalactosamine and the hexasaccharide GlcNAc(beta 1-6) [GalNAc(alpha 1-3)( Fuc (alpha 1-2)]Gal(beta 1-4)GlcNAc(beta 1-3)]GalNAcol (Fuc, L-fucose). Oligosaccharides of the blood-group-A type have not been detected previously in bovine submaxillary-gland mucin although their occurrence on bovine gastric-mucosal glycoproteins has been established by classical immunochemical studies.