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G Ekborg

Publications and source records attributed to G Ekborg.

12 recordsLinked to original sources
PubMed1997

Analysis of the Morgan-Elson chromogens by high-performance liquid chromatography.

The Morgan-Elson method for quantitative N-acetylhexosamine analysis is a two-step procedure comprising alkali treatment of the sugar and subsequent condensation of the resulting chromogens with p-dimethylaminobenzaldehyde (Ehrlich's reagent) to yield a colored product. In the present investigation, the products formed in the first step of the procedure were analyzed by high-performance liquid chromatography (HPLC) on a reversed-phase (C18) column, which was eluted with a water-methanol gradient; the absorbance of the effluent was monitored at 229 nm. The profile generated from alkali-treated N-acetylglucosamine exhibited two major peaks, in a ratio of approximately 2.5:1, which accounted for 94% of the total peak area. A third peak, accounting for 3% of the peak area, was eluted in an intermediate position, and several smaller peaks were also observed. The three predominant components, isolated by preparative HPLC, all gave a purple color on addition of Ehrlich's reagent, indicating that they were Morgan-Elson chromogens. The HPLC profile of alkali-treated N-acetylmannosamine was identical to that of the products generated from N-actylglucosamine, as was expected because of the elimination of the asymmetry at C-2 during formation of the chromogens. N-Acetylgalactosamine yielded two major peaks, which were eluted in the same positions as the two major products formed from N-acetylglucosamine, but the intermediate peak seen in the N-acetylglucosamine pattern was absent. The HPLC procedure allowed detection of as little as approximately 25 ng of N-acetylglucosamine and may therefore be of value as an alternative to the complete Morgan-Elson procedure when only small amounts of sample are available for quantitative analysis.

Acetylgalactosamine↗
PubMed1991

Glucuronosyl transfer to galactose residues in the biosynthesis of HNK-1 antigens and xylose-containing glycosaminoglycans: one or two transferases?

An early step in the assembly of the xylose----serine-linked proteoglycans is the transfer of glucuronic acid to the C-3 position of a galactose residue in the carbohydrate-protein linkage region. Since a similar reaction occurs in the biosynthesis of NHK-1 antigens, the question arose whether these processes are catalyzed by the same enzyme. In the present study, the proteoglycan-related glucuronosyltransferase activity in embryonic chick brain was found to be firmly membrane-associated, while the majority of the activity towards N-acetyllactosamine - a model substrate for HNK-1 antigen biosynthesis - was readily solubilized. No activity towards N-acetyllactosamine was found in embryonic chick cartilage, which is a rich source of the proteoglycan-related enzyme. Together with the results of mixed substrate experiments, these findings strongly indicate the existence of two separate glucuronosyltransferases catalyzing transfer to galactose residues.

Animals↗
PubMed1987

Inhibition of chondroitin and heparan sulfate biosynthesis in Chinese hamster ovary cell mutants defective in galactosyltransferase I.

We have isolated five Chinese hamster ovary cell mutants defective in galactosyltransferase I (UDP-D-galactose:xylose beta-1,4-D-galactosyltransferase) and studied the effect of p-nitrophenyl-beta-D-xyloside supplementation on glycosaminoglycan biosynthesis in the mutant cells. Assays of galactosyltransferase I showed that the mutants contained less than 2% of the enzyme activity present in wild-type cells, and enzyme activity was additive in mixtures of mutant and wild-type cell extracts, suggesting that the mutations most likely defined the structural gene encoding the enzyme. Cell hybridization studies showed that the mutations in all five strains were recessive and that the mutants belonged to the same complementation group. The mutants contained wild-type levels of xylosyltransferase (UDP-D-xylose:core protein (serine) beta-D-xylosyltransferase), lactose synthase (UDP-D-galactose:N-acetyl-glucosaminide beta-1,4-D-galactosyltransferase), and lactosylceramide synthase (UDP-D-galactose:glucosylceramide beta-1,4-D-galactosyltransferase). Their sensitivity to lectin-mediated cytotoxicity was virtually identical to that of the wild-type, indicating that there were no gross alterations in glycoprotein or glycolipid compositions. Anion-exchange high performance liquid chromatography of 35S-glycosaminoglycans from one of the galactosyltransferase I-deficient mutants showed a dramatic reduction in both heparan sulfate and chondroitin sulfate, demonstrating that galactosyltransferase I is responsible for the formation of both glycosaminoglycans in intact cells. Surprisingly, the addition of 1 mM-p-nitrophenyl-beta-D-xyloside, a substrate for galactosyltransferase I, restored glycosaminoglycan synthesis in mutant cells. This finding suggested that another galactosyltransferase, possibly lactose synthase, can transfer galactose to xylose in intact cells.

Animals↗
PubMed1985

Synthesis of p-nitrophenyl beta-glycosides of (1----6)-beta-D-galactopyranosyl-oligosaccharides.

Sequential tritylation, benzoylation, and detritylation of p-nitrophenyl beta-D-galactopyranoside gave p-nitrophenyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (2). Reaction of 2 with 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide gave p-nitrophenyl O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----6) -2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (4) in 94% yield. Deprotection with sodium methoxide then gave the crystalline p-nitrophenyl O-(beta-D-galactopyranosyl)-(1----6)-beta-D-galactopyranoside (5). Condensation of 2 with 2,3,4-tri-O-benzoyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide (3) readily yielded the protected disaccharide p-nitrophenyl O-(2,3,4-tri-O-benzoyl-6-O-bromoacetyl-beta-D-galactopyranosyl)-(1----6) -2,3,4-tri-O-benzoyl-beta-D-galactopyranoside (6) from which the bromoacetyl groups could be selectively removed. Condensation of the resulting material with tetra-O-benzoyl-alpha-D-galactopyranosyl bromide then yielded p-nitrophenyl O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----6)-O-(2,3,4 -tri-O-benzoyl-beta-D-galactopyranosyl)-(1----6)-2,3,4-tri-O-benzoyl-bet a-D -galactopyranoside, (8), which was converted into the crystalline trisaccharide p-nitrophenyl O-(beta-D-galactopyranosyl)-(1----6)-O-beta-D-galactopyranosyl)-(1----6) -beta -D-galactopyranoside (9) by treatment with sodium methoxide. Preliminary experiments on the interaction of p-(bromoacetamido)phenyl and p-isothiocyanatophenyl glycoside derivatives of some of these galacto-saccharides with monoclonal anti-(1----6)-beta-D-galactopyranan antibodies have been conducted.

Antibodies, Monoclonal↗
PubMed1985

p-Trifluoroacetamidophenyl O-alpha-D-mannopyranosyl-(1----3)-O-[alpha-D-mannopyranosyl- (1----6)]-beta-D-mannopyranoside.

p-Nitrophenyl 2-O-benzyl-4,5-O-cyclohexylidene-beta-D-mannopyranoside (4) was condensed with tetra-O-benzoyl-alpha-D-mannopyranosyl bromide. The resulting, protected disaccharide was converted into p-nitrophenyl O-(2,3,4-tri-O-benzoyl-alpha-D-mannopyranosyl)-(1----3)-4-O-benzoyl-2-O- benzyl-beta-D-mannopyranoside (8), which was condensed with tetra-O-benzoyl-alpha-D-mannopyranosyl bromide to give p-nitrophenyl O-(2,3,4-tri-O-benzoyl-alpha-D-mannopyranosyl)-(1----3)-O -[2,3,4-tri-O-benzoyl-alpha-D-mannopyranosyl-(1----6)]-4-O-benzoyl-2-O -benzyl-beta-D-mannopyranoside (9) in 75% yield. Conversion of the p-nitrophenyl group followed by deprotection then yielded the title compound, whose structure was confirmed by 1H- and 13C-n.m.r. spectroscopy.

Hydrogen-Ion Concentration↗
PubMed1983

Monoclonal IgA J539 binds galactopyranosyl antigens on its surface.

Murine monoclonal IgA J539 binds to methyl beta-D-galactopyranoside. With nearly the same affinity, it binds to methyl 6-O-pivaloyl-beta-D-galactopyranoside (4) and to methyl 6-O-beta-D-gentiobiosyl-beta-D-galactopyranoside (7). These observations confirm that the combining area of J539 is of the surface-, and not of the cavity-type.

Animals↗
PubMed1982

Synthesis of three disaccharides for the preparation of immunogens bearing immunodeterminants known to occur on glycoproteins.

p-Nitrophenyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside was condensed with 2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl bromide, the product deprotected, and the disaccharide glycoside converted into p-trifluoroacetamidophenyl 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-beta- D-glucopyranoside. p-Nitrophenyl 3-O-benzoyl-4,6-di-O-benzylidene-alpha-D-mannopyranoside was condensed with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl bromide, and the product was deprotected, to yield p-nitrophenyl 2-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-alpha-D-mannopyranoside. p-Nitrophenyl 2-acetamido-3,4-di-O-benzoyl-2-deoxy-beta-D-glucopyranoside was condensed with 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl bromide, and, after reduction, trifluoroacetylation, and deprotection, p-trifluoroacetamidophenyl 2-acetamido-2-deoxy-6-O-alpha-L-fucopyranosyl-beta-D-glucopyranoside was obtained.

Antigens↗