Structural investigation of a glycoprotein from gum ghatti.

The glycoprotein structure of gum ghatti was investigated. The covalent bonding between polysaccharides and proteins was firstly confirmed by high performance size exclusion chromatography (HPSEC) using refractive index (RI) and UV detectors. Partial acid hydrolysis and enzymatic degradation were also utilized. Several structural fragments such as AraHex2-HexA-HexNAc, Hex4HexNAc2, AraHex4HexNAc, Hex10HexNAc and Hex4HexNAc-Asn were identified from MALDI-TOF spectrum; using 1D and 2D NMR spectra, the linkage site of amino acids and polysaccharides was determined as N-linked (Hex)n-GlcNAc-Asn. Combined with the polysaccharide structure obtained before, a glycoprotein structure model was proposed. It was composed of 1,6-linked galactose backbone, which were attached by numerous of sugar side chains and peptide chains.