Primary structure of four human milk octa-, nona-, and undeca-saccharides established by 1H- and 13C-nuclear magnetic resonance spectroscopy.

The structures of two octasaccharides, one nonasaccharide, and one undecasaccharide, isolated from human milk, have been investigated by 1H- and 13C-nuclear magnetic resonance spectroscopy. The structures of these oligosaccharides are: beta-D-Galp-(1----4)-[alpha-L-Fucp- (1----3)]-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-[alpha-L-Fucp+ ++- (1----3)]-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-D-Glc; beta-D-GALp-(1----3)-[alpha-L-Fucp-(1----4)]-beta-D-GlcpNAc-(1---- 3)-beta-D - Galp-(1----4)-[alpha-L-Fucp-(1----3)]-beta-D-GlcpNAc-(1----3)-beta -D-Galp- (1----4)-D-Glc; beta-D-Galp-(1----4)-[alpha-L-Fucp-(1----3)]-beta-D-GlcpNAc-(1---- 6)-(alpha - L-Fucp-(1----2)-beta-D-Gal-(1----3)-[alpha-L-Fucp-(1----4)]- beta-D-GlcpNAc- (1----3))-beta-D-Galp-(1----4)-D-Glc; and alpha-L-Fucp-(1----2)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3) -beta-D- Galp-(1----4)-[alpha-L-Fucp-(1----3)]-beta-D-GlcpNAc-(1----6)-[alp ha-L- Fucp-(1----2)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3)]-beta-D -Galp- (1----4)-D-Glc. The two octasaccharides have been previously isolated from human milk as a mixture, and in a pure form from new-born feces, but the n.m.r. data were not provided. These two octasaccharides display the di-Lewis X and the composite Lewis A-Lewis X antigenic determinant, previously described as neo-antigens of adenocarcinoma cell lines.     

Elongation of both branches of biantennary backbones of oligo-(N-acetyllactosamino)glycans by human serum (1----3)-N-acetyl-beta-D- glucosaminyltransferase.

Partial reactions catalyzed by a (1----3)-N-acetyl-beta-D- glucosaminyltransferase (EC2.4.1.149), known to be present in human serum, were studied by use of biantennary "backbone" saccharides of oligo-N-acetyllactosamine-type as acceptors. Incubation of the radiolabeled blood-group I-active hexasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp- (1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-GlcNAc (1) and UDP-GlcNAc with serum gave first a transient 1:1 mixture of two isomeric heptasaccharides, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D- GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D- Galp-(1----4)-D-GlcNAc (2) and beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-GlcpNAc-(1----3)- beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-Glc NAc (3), showing that both branches of 1 react equally well. The two heptasaccharides reacted further in the incubation mixture to form the radiolabeled octasaccharide, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[be ta-D- GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Ga lp- (1----4)-D-GlcNAc (4); during this second reaction, the composition of the heptasaccharide mixture remained unchanged, indicating that 2 and 3 reacted at approximately equal rates. The heptasaccharides 2 and 3 could not be separated from each other, but they could be detected, identified, and quantitatively determined by stepwise enzymic degradations. Partial (1----3)-N-acetyl-beta-D-glucosaminylation reactions, carried out with another acceptor, the branched pentasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta- D- GlcpNAc-(1----6)]-beta-D-Gal (11), revealed that it reacted also equally well at both branches.(ABSTRACT TRUNCATED AT 400 WORDS)     

Further definition of the size of the blood group-i antigenic determinant using a chemically synthesised octasaccharide of poly-N-acetyllactosamine type.

In earlier studies, the minimum structure which inhibited the binding of anti-i to an i-active glycoprotein was the linear trisaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-D-Gal. There was an increasing hierarchy of inhibitory activities in the linear tetrasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D -GlcNAc , its methyl beta-glycoside, and in the methyl beta-glycoside of the hexasaccharide. The linear octasaccharide methyl beta-glycoside in this series is approximately only half as active as the hexasaccharide methyl beta-glycoside. Analyses by high resolution 1H-n.m.r. of these two oligosaccharides indicated that they have similar conformations in solution, and there is no evidence for the occurrence of inter-molecular interactions which might partially hinder the binding of anti-i to the octasaccharide methyl beta-glycoside. These results are consistent with the size of the i antigen being in the region of a hexasaccharide. It is proposed that the methyl aglycon group of the hexasaccharide methyl beta-glycoside confers an above normal activity by presenting a hydrophobic area for additional contact in the vicinity of the antibody-combining site.     

Complete 1H- and 13C-n.m.r. assignments for two sulphated oligosaccharide alditols of hen ovomucin

The complete 1H- and 13C-n.m.r. assignments for beta-D-Galp-(1----4)-beta-D-GlcpNAc-6-SO3H-(1----6)-[beta-D-Galp-(1----3 )]- D-GalNAcol and alpha-NeuAcp-(2----3)-beta-D-Galp-(1----3)-[beta-D-Galp-(1----4)-b eta-D- GlcpNAc-6-SO3H-(1----6)]-D-GalNAcol were made by a combination of 2-D correlation experiments (Relayed-Cosy; and 13C,1H Correlation-shift n.m.r. spectroscopy), and 1-D n.m.r. spectroscopy. The results illustrate the ability of these methods to locate sulphate and NeuAc groups in anionic mucinous glycoproteins.     

Chemo-enzymatic synthesis of a tetra- and octasaccharide fragment of the capsular polysaccharide of Streptococcus pneumoniae type 14

The chemo-enzymatic synthesis is described of tetrasaccharide beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->6)-[beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->O(CH(2))(6)NH(2) (1) and octasaccharide beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->6)-[beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->6)-[beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->O(CH(2))(6)NH(2) (2), representing one and two tetrasaccharide repeating units of Streptococcus pneumoniae serotype 14 capsular polysaccharide. In a chemical approach, the intermediate linear trisaccharide 3 and hexasaccharide 4 were synthesized. Galactose residues were beta-(1-->4)-connected to the internal N-acetyl-beta-D-glucosamine residues by using bovine milk beta-1,4-galactosyltransferase. Both title oligosaccharides will be conjugated to carrier proteins to be tested as potential vaccines in animal models.     

Biosynthesis of the blood group Pk and P1 antigens by human kidney microsomes.

On human erythrocytes, the membrane components associated with Pk and P1 blood-group specificity are glycosphingolipids that carry a common terminal alpha-D-Galp-(1----4)-beta-D-Gal unit, the biosynthesis of which is poorly understood. Human kidneys typed for P1 and P2 (non-P1) blood-group specificity have been assayed for (1----4)-alpha-D-galactosyltransferase activity by use of lactosylceramide [beta-D-Galp-(1----4)-beta-D-Glcp-ceramide] and paragloboside [beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-beta-D-Galp- (1----4)-beta-D-Glcp-ceramide] as acceptor substrates. The linkage and anomeric configuration of the galactosyl group transferred into the reaction products were established by methylation analysis before and after alpha- and beta-D-galactosidase treatments, as well as by immunostaining using specific monoclonal antibodies directed against the Pk and P1 antigens. The results demonstrated that the microsomal proteins from P1 kidneys catalyze the synthesis of Pk [alpha-D-Galp-(1----4)-beta-D-Galp-(1----4)-beta-D-Glcp-ceramide] and P1 [alpha-D-Galp-(1----4)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-beta -D-Galp-(1----4)-beta-D-Glcp-ceramide] glycolipids, whereas microsomes from P2 kidney catalyze the synthesis of the Pk glycolipid, but not of the P1 glycolipid. Competition studies using a mixture of two oligosaccharides (methyl beta-lactoside and methyl beta-lacto-N- neotetraoside) or of two glycolipids (lactosylceramide and paragloboside) as acceptors indicated that these substrates do not compete for the same enzyme in the microsomal preparation from P1 kidneys. The results suggested that the Pk and P1 glycolipids are synthesized by two distinct enzymes.     

Primary structure of ten galactosides formed by transglycosylation during lactose hydrolysis by Bifidobacterium bifidum

Oligosaccharides formed by a transgalactosylation reaction during lactose hydrolysis with Bifidobacterium bifidum were separated into eight fractions by gel-permeation chromatography and their structures studies determined by trimethylsilylation analysis, methylation analysis, f.a.b.-m.s., g.l.c.-m.s. and enzymic hydrolysis as beta-D-Galp-(1----3)-D-Glc, beta-D-Galp-(1----6)-D-Glc, beta-D-Galp-(1----6)-D-Gal, beta-D-Galp-(1----3)-beta-D-Galp-(1----4)-D-Glc, beta-D-Galp-(1----6)[beta-D-Galp-(1----4)]-D-Glc, beta-D-Galp-(1----2)[beta-D-Galp-(1----6)]-D-Glc, beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-beta-D-Galp-(1----4)-D-Glc, beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-beta-D-Ga lp- (1----4)-D-Glc, beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-beta-DGalp-(1----3)-beta -D-Galp-(1----3)-beta-D-Galp-(1----4)-D-Glc, and beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-beta-D-Ga lp-(1----3)-beta-D-G-alp-(1----3) beta-D-Galp-(1----4)-D-Glc.     

Chemo-enzymatic synthesis of tetra-, penta-, and hexasaccharide fragments of the capsular polysaccharide of Streptococcus pneumoniae type 14

The chemo-enzymatic synthesis is described of beta-D-Glcp-(1-->6)-[beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->3)-beta-D-Galp-(1-->O(CH(2))(6)NH(2) (1), beta-D-Glcp-(1-->6)-[beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->O(CH(2))(6)NH(2) (2), beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->O(CH(2))(6)NH(2) (3), and beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->6)-[beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->O(CH(2))(6)NH(2) (4), representing fragments of the repeating unit of the Streptococcus pneumoniae serotype 14 capsular polysaccharide. Linear intermediate oligosaccharides 5-8 were synthesized via chemical synthesis, followed by enzymatic galactosylation using bovine milk beta-1,4-galactosyltransferase as a catalyst. The title oligosaccharides form suitable compounds for conjugation with carrier proteins, to be tested as potential vaccines in animal models.     

Binding studies on internal immunodeterminants: synthesis of beta-(1----6)-linked oligosaccharide methyl glycosides having one to four internal D-galactopyranosyl residues flanked by gentiobiose residues.

The oligosaccharide glycosides beta-D-Glcp-(1----6)-beta-D-Glcp-(1----6)-[beta-D-Galp-(1----6)]n-beta-D - Glcp-(1----6)-beta-D-Glcp-1----OMe (n = 1-4) were prepared by a convergent block synthesis. Haloacetyl, tert-butyldiphenylsilyl, and dimethylthexylsilyl groups were used as temporary protective groups for the preparation of the intermediate glycosyl donors and acceptors. The deoxygenated trisaccharide glycosides beta-D-Glcp-(1----6)-beta-D-Galp-(1----6)-4-deoxy-beta-D-xylo-Hexp -1----OMe and beta-D-Glcp-(1----6)-4-deoxy-beta-D-xylo-Hexp-(1----6)-beta-D-Galp -1----OMe were also synthesized. The binding of each glycoside to the monoclonal antigalactan antibody IgA J539 was studied and the results support the previous finding that J539 can bind to internal antigenic epitopes. The data are consistent with the interpretation that subsite C of that antibody binds glucose with a Ka of approximately 6 (cf. 10.9 for galactose).     

Synthesis of the methyl and 1-octyl glycosides of the P-antigen tetrasaccharide (globotetraose)

The methyl and 1-octyl beta-glycosides of the P-antigen tetrasaccharide [globotetraose, beta-D-GalpNAc-(1----3)-alpha-D-Galp-(1----4)-beta-D-Galp-(1----4) -D-Glc] were synthesised from a tetrasaccharide precursor, prepared using methyl disaccharide 1-thioglycosides as intermediates. In the key glycosidation with silver triflate, HO-2 was used as an alpha-directing group in the glycosyl bromide.     

Analysis of the interaction between lectins and tetra- and tri-saccharide mimics of the Sd(a) determinant by surface plasmon resonance detection

The binding properties of a spacer-linked synthetic Sd(a) tetrasaccharide beta-D-GalpNAc-(1-->4)-alpha-Neu5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (1), two tetrasaccharide mimics beta-D-Galp-(1-->4)-alpha-Neu5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (2) and beta-D-GlcpNAc-(1-->4)-alpha-Neu5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (3), and two trisaccharide mimics beta-D-GalpNAc-(1-->4)-3-O-(SO(3)H)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (4) and beta-D-GalpNAc-(1-->4)-3-O-(CH(2)COOH)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (5) with lectins from Dolichos biflorus (DBL), Maackia amurensis (MAL), Phaseolus limensis (PLL), Ptilota plumosa (PPL), Ricinus communis 120 (RCL120) and Triticum vulgaris (wheat germ agglutinin, WGA) have been investigated by surface plasmon resonance (SPR) detection. MAL, PPL, RCL120 and WGA did not display any binding activity with compounds 1-5. However, DBL and PLL, both exhibiting GalNAc-specificity, showed strong binding activity with compounds 1, 4 and 5, and 1, 3, 4 and 5, respectively. The results demonstrate that SPR is a very useful analysis system for identifying biologically relevant oligosaccharide mimics of the Sd(a) determinant.     

Synthesis of the Lewis b hexasaccharide and squarate acid-HSA conjugates thereof with various saccharide loadings

The Lewis b hexasaccharide, alpha-L-Fucp-(1 --> 2)-beta-D-Galp-(1 --> 3)-[alpha-L-Fucp-(1 --> 4)]-beta-D-GlcpNAc-(1 --> 3)-beta-D-Galp-(l --> 4)-beta-D-Glcp, has been synthesised using a convergent synthesis. Starting from ethyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-1-thio-beta-D-glucopyranoside, a thioglycoside tetrasaccharide donor block, was constructed through two orthogonal glycosylations with glycosyl bromide donors. First, the galactose moiety was introduced using silver triflate as a promoter and then the two fucose residues under halide-assisted conditions. Finally, this tetrasaccharide was linked to a spacer-equipped 3I,4I-diol lactose acceptor in a DMTST-promoted coupling to give, after deprotection, the Lewis b hexasaccharide as its 2-aminoethyl spacer-equipped derivative. This was coupled to human serum albumin (HSA), using the squarate ester methodology, in various saccharide-protein ratios, to give neoglycoconjugates with different saccharide loadings in about 50%) efficiency.     

A synthetic heptasaccharide reveals the capability of a monoclonal antibody to read internal epitopes of a polysaccharide antigen.

The binding of the synthetic heptasaccharide,beta-D-Galp-(1----3)-beta-D-Galp-(1----6)-beta-D-Galp-(1 ----6)-beta-D-Galp-(1----6)-beta-D-Galp-1-OCH3 (10) with two monoclonal IgAs of the X24 gene-family has been investigated. The ligand 10 was synthesized by silver triflate mediated coupling of O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----3)-O-(2,4,6,-t ri-O-benzoyl-beta-D-galactopyranosyl)-(1----3)-2,4,6-tri-O-benzoyl-alpha -D-galactopyranosyl chloride (5) to the benzoylated, all-beta-(1----6)-linked methyl galactotetraoside 13, having O-6(4) free, followed by debenzoylation of the formed, fully protected methyl galactoheptaoside. The blockwise synthesis of the nucleophile 13 from readily available monosaccharides, and the synthesis of 5 from the corresponding beta-1-O-benzoylated trisaccharide, is also described. Heptasaccharide 10 binds with the (1----6)-beta-D-galactan-specific monoclonal antibodies X-24 and J539 with essentially the same Ka-values (5.4 x 10(5) M-1 and 6.4 x 10(5) M-1, respectively) as does the methyl beta-glycoside of all-beta-(1----6)-linked galactotetraose 14 (5.7 x 10(5) M-1 and 5.9 x 10(5) M-1, respectively). Of the series of homologous oligosaccharides studied previously (di- through a hexa-saccharide), 14 was found to show the highest affinity of interaction with both these immunoglobulins. The beta-(1----3)-linked galactotriose, which forms the bulky terminus of 10, does not appear to bind to these IgA. Thus, the observation that the affinity of 10 is the same as that of 14 confirms that these immunoglobulins bind internal tetrasaccharide sequences of the antigenic (1----6)-beta-D-galactopyranan.     

The structure of the asparagine-linked sugar chains of bovine brain ribonuclease

The asparagine-linked sugar chains of bovine brain ribonuclease were quantitatively released as oligosaccharides from the polypeptide backbone by hydrazinolysis. After N-acetylation, they were converted into radioactively-labeled oligosaccharides by NaB3H4 reduction. The radioactive oligosaccharide mixture was fractionated by ion-exchange chromatography, and the acidic oligosaccharides were converted into neutral oligosaccharides by sialidase digestion. The neutral oligosaccharides were then fractionated by Bio-Gel P-4 column chromatography. Structural studies of each oligosaccharide by sequential exoglycosidase digestion in combination with methylation analysis revealed that bovine brain ribonuclease showed extensive heterogeneity. It contains bi- and tri-antennary, complex-type oligosaccharides having alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp -(1----4)-beta-D- GlcpNAc-(1----4)-[alpha-L-Fucp-(1----6)]-D-GlcNAc as their common core. Four different outside oligosaccharide chains, i.e., beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----, alpha-Neu5Ac-(2----6)-beta-D- Galp-(1----4)-beta-D-GlcpNAc-(1----, alpha-Neu5Ac-(2----3)-beta-D-Galp-(1----4)- beta-D-GlcpNAc-(1----, and alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----, were found. The preferential distribution of the alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc group on the alpha-D-Manp-(1----6) arm is a characteristic feature of the sugar chains of this enzyme.     

Synthesis of alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D-Manp+ ++-(1----6)] - beta-D-Manp-(1----4)-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp- (1----6)]-D- GlcpNAc, a core glycoheptaose of a "bisected" complex-type glycan of glycoproteins

A synthesis of alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D-Manp++ +-(1----6)]- beta-D-Manp-(1----4)-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp-( 1----6)]-D- GlcpNAc was achieved by employing benzyl O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--- -4)-O- (2-O-benzyl-beta-D-mannopyranosyl)-(1----4)-O-(3,6-di-O-benzyl-2-deoxy-2 - phthalimido-beta-D-glucopyranosyl)-(1----4)-3-O-benzyl-2-deoxy-6-O-p- methoxyphenyl-2-phthalimido-beta-D-glucopyranoside as a key glycosyl acceptor. Highly stereoselective mannosylation was performed by taking advantage of the 2-O-acetyl group in the mannosyl donors. The alpha-L-fucopyranosyl residue was also stereoselectively introduced by copper(II)-mediated activation of methyl 2,3,4-tri-O-benzyl-1-thio-beta-L-fucopyranoside.     

Enzymic synthesis of oligosaccharides terminating in the tumor-associated sialyl-Lewis-a determinant

The isomeric sialyl-Lea-terminating pentasaccharide derivatives, alpha-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-[alpha-L-Fucp-(1 ----4)]-beta- D-GlcpNAc-(1----3)-beta-D-Galp-O(CH2)8COOMe and alpha-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-[alpha-L-Fucp-(1 ----4)]- beta-D-GlcpNAc-(1----6)-beta-D-Galp-O(CH2)8COOMe, have been prepared by the action in sequence of a porcine submaxillary (2----3)-alpha-sialyltransferase and a human-milk (1----3/4)-alpha-fucosyltransferase on the chemically synthesized trisaccharides beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3)- and -(1----6)-beta-D-Galp- O(CH2)8COOMe, respectively.     

Facile synthesis of a pentasaccharide mimic of a fragment of the capsular polysaccharide of Streptococcus pneumoniae type 15C

A pentasaccharide mimic of a fragment of the capsular polysaccharide of Streptococcus pneumoniae type 15C beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->6)-[alpha-D-Galp-(1-->2)-beta-D-Galp-(1-->4)]-beta-D-GlcpNAc-(1-->OCH2CH2N3) (1) was synthesized in a regio- and stereoselective manner. The 2-azidoethyl-spacered pentasaccharide mimic 1 can be used to construct a neoglycoconjugate antigen.     

The use of porcine liver (2----3)-alpha-sialyltransferase in the large-scale synthesis of alpha-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-D-GlcpNAc, the epitope of the tumor-associated carbohydrate antigen CA 50.

alpha-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-D-GlcpNAc (2) and, alpha-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-beta-D-GlcpNAcOMBn+ ++ were prepared on a large scale by the action of beta-D-Galp-(1----3)-D-GalpNAc (2----3)-alpha-sialyltransferase (partially purified from porcine liver) on beta-D-Galp-(1----3)-D-GlcpNAc and beta-D-Galp-(1----3)-beta-D-GlcpNAcOMBn, respectively. The trisaccharide 2 is the epitope of the tumor-associated carbohydrate antigen CA 50, highly expressed in human pancreatic adenocarcinoma.     

Biosynthesis of disialylated beta-D-galactopyranosyl-(1----3)-2-acetamido-2-deoxy-beta-D-glucopy ran osyl oligosaccharide chains. Identification of a beta-D-galactoside alpha-(2----3)- and a 2-acetamido-2-deoxy-beta-D-glucoside alpha-(2----6)-sialyltransferase in regenerating rat liver and other tissues

Regenerating rat liver microsomes contain a beta-D-galactoside alpha-(2----3)- and a 2-acetamido-2-deoxy-beta-D-glucoside alpha-(2----6)-sialyltransferase that are involved in the synthesis of the terminal alpha-NeuAc-(2----3)-beta-D-Galp-(1----3)-alpha-[NeuAc-(2----6)]-beta- D-GlcpNAc-(1----R) group occurring in human milk oligosaccharides and the glycan chains of several N-glycoproteins. Analysis by liquid chromatography and methylation of the products of sialylation obtained when lacto-N-tetraose [beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4) -D-Glc] was used as a substrate in the incubations in vitro indicated that the disialylated sequence is formed for greater than 95% through the tetrasaccharide alpha-NeuAc-(2----3)-beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----3)-beta-D-G al- (1----4)-D-Glc as one of two possible intermediates. This indicates that in the synthesis of the disialylated sequence the alpha-(2----3)- and the alpha-(2----6)-sialyltransferase act in a highly preferred order in which the alpha-(2----3) enzyme acts first. This order is imposed by the specificity of the alpha-(2----6)-sialyltransferase, which requires an alpha-NeuAc-(2----3)-beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----R) sequence for optimal activity, and shows very low and no activity with beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----R) and beta-D-GlcNAc-(1----R) acceptor structures, respectively. Results obtained with normal rat, fetal calf, rabbit and human liver, and human placenta indicated that very similar or identical sialyltransferases occur in these tissues. It is suggested that these enzymes differ from the sialyltransferases that previously had been identified in fetal calf liver and human placenta.     

Initiation of poly-N-acetyllactosamine chain biosynthesis occurs preferentially on complex multiantennary asparagine-linked oligosaccharides

An N-acetyl-beta-D-glucosaminyltransferase activity involved in the initiation of poly-N-acetyllactosamine chain biosynthesis can be solubilized from Ehrlich ascites tumor cell microsomal membranes. The ability of this enzyme to act on linear and branched acceptor substrates has been studied. The results indicate that complex-type tri- and tetra-antennary oligosaccharides exhibiting the branching pattern beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)-[beta-D-Galp-(1----4)-beta- D- Glcp-NAc-(1----2)]-D-Man are the preferred substrates for the enzyme, and therefore, may represent the structures upon which the generation of poly-N-acetyllactosamine chains proceeds more efficiently.