Glycosidic linkages to the hydroxyl

Glycosidic Linkages to the Hydroxyl Groups of Serine and Threonine Residues... 

Direct proof for the existence of O-glycosidic linkages involving the hydroxyl groups of serine and threonine was provided simultaneously from three laboratories. Anderson et al. (39) reported partial losses of serine and threonine after treatment with 0.52V NaOH (or 0.452V KOH) at 4°C or room temperature for about 20 hours. Subsequent reduction with platinum showed formation of some alanine and < -aminobutyric acid. Harbon et al (40) treated ovine submaxillary glycoprotein at pH 12.8 for 45 minutes at 70 °C. The serine and threonine content decreased by 78 and 60%, respectively. Treatment of this product with 0.1M sulfite, (pH 9, 24 hours, room temperature) caused a conversion of the dehydroserine residues to cysteic acid, but had no action on the dehydrothreonine residues. This reaction has been further studied by Simpson et al. (41). 

The major component of all known bacterial cell walls is a polysaccharide composed of Af-acetyl-D-glucosamine (NAG) linked together by 8-(l— 4) glycosidic bonds, as in chitin, but with every other NAG residue substituted at C-3 by an ether linkage to the hydroxyl group of L-lactic acid to give N-acetyl-D-muramic acid (NAM) [85,86,87,88]. This results in a nine-... 

The anomeric-carbon region shows six peaks, numbered in Fig. 4. Peak 1 (at 103.6 p.p.m.), which arises from 25 5 carbon atoms, can be assigned to the anomeric-carbon atoms of a-D-mannopyranosyl units, having free hydroxyl groups at C-2, that are involved in glycosidic linkages to 0-2 or 0-3 of other a-D-mannopyranosyl residues.15 Peak 2 (at 102.5 p.p.m.) probably arises from 2-O-substituted a-D-mannopyrano-syl units involved in linkages to 0-2 or 0-3 of other a-D-mannopyranosyl units (internal carbohydrates)15 and also to the anomeric carbon atom of the a-D-mannopyranosyl residue linked to L-threonine.19 Peak 3 (101.8 p.p.m.) arises from the a-D-mannopyranosyl unit linked to L-ser-ine.19... 

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