The structure of the glycopeptides from the fish pathogen Flavobacterium columnare

摘要

Proteolytic digestion of the phenol-water extraction product of the fish pathogen Flavobacterium columnare afforded a mixture of glycopeptides in which the oligosaccharide moiety was an unusual hexasaccharide composed of 4-O-methyl-2-acetamido-2-deoxy-D-glucuronic acid (GlcNAcA),D-glucuronic acid (D-GlcA),2,3-di-O-acetyl-D-xylose (D-Xyl),2-O-methyl-D-glucuronic acid (D-GlcA),D-mannose (D-Man),and 2-O-methyl-L-rhamnose (L-Rha).By the application of high-resolution 1D and 2D NMR,mass spectrometry,and chemical analysis,the hexasaccharide structure was determined to be:where all monosaccharides have the D-configuration except for 2-O-methyl-L-rhamnose;and were in the pyranose form.Only one carbohydrate structure was found.The peptide part was represented by tri-to hepta-peptides with a minimal common tripeptide fragment Asp-Ser-Ala,extended with Ala and Val.