The 5-O-/3-D-Galactofuranosyl-containing Glycopeptide from Penicillium charlesii

Natural abundance carbon 13 nuclear magnetic resonance spectroscopy was used to confirm and extend the structural properties of peptidophosphogalactomannan (pPGM) from Penicillium charlesii. The major resonances for phosphogalactomannan (PGM) and phosphomannan (PM) were assigned. Based on comparison of chemical shifts of carbon 13 resonance signals in phosphogalactomannan with those of galactocarolose, malonogalactan and the four methygalactosides, we conclude that all of the galactosyl residues are in the furanosyl form and are attached by /3(1+ 5)0-glycosidic linkages. One-bond C-H coupling constants confirm that galactose is in the furanosyl form. NMR data strongly supports the claim that the mannopyranosyl residues are o-linked. A resonance at 75.9 ppm, characteristic of C5 of an a-mannopyranoside, was found, whereas there was no resonance at 79 ppm, characteristic of C5 of a fi-mannopyranoside. The carbon 13 chemical shifts of the mannan are consistent with (1 + 2)-0-glycosidic linkages joining mannosyl residues. A resonance at 103.2 ppm coincides precisely with that of the anomeric carbon of the internal sugar of 0-cw-D-mannopyranosyl-(1 + 2)-O-a-D-maImOpyranosyl-(1 -+ 2)-n-mannose. Moreover, resonance signals from the mannan portion of peptidophosphogalactomannan occur at similar positions as carbons 2,3,4,5, and 6 of the same internal 2-O-substituted mannosyl unit. Alkali-treated glycopeptide has two doublets in identical positions to the resonances of the methylene carbons of (Y-Lglycerophosphorylethanolamine, with splitting as a result of 13C31P coupling. This suggests that ethanolamine is attached to the mannan through a phosphodiester linkage.