Structural features of N-glycans linked to royal jelly glycoproteins:: Structures of high-mannose type, hybrid type, and biantennary type glycans

The structures of N-glycans of total glycoproteins in royal jelly have been explored to clarify whether antigenic N-glycans occur in the famous health food, The structural feature of N-glycans linked to glycoproteins in royal jelly was first characterized by immunoblotting with an antiserum against plant complex type N-glycan and lectin-blotting with Con A and WGA, For the detail structural analysis of such N-glycans, the pyridylaminated (PA-) N-glycans were prepared from hydrazinolysates of total glycoproteins in royal jelly and each PA-sugar chain was purified by reverse-phase HPLC and size-fractionation HPLC, Each structure of the PA-sugar chains purified was identified by the combination of two-dimensional PA-sugar chain mapping, ESI-MS and MS/MS analyses, sequential exoglycosidase digestions, and 500 MHz H-1-NMR spectrometry. The immunoblotting and lectinblotting analyses preliminarily suggested the absence of antigenic N-glycan bearing beta1-2 xylosyl and/or alpha1-3 fucosyl residue(S) and occurrence of beta1-4GlcNAc residue in the insect glycoproteins. The detailed structural analysis of N-glycans of total royal jelly glycoproteins revealed that the antigenic N-glycans do not occur but the typical high mannose-type structure (Man(9-4)GlcNAc(2)) occupies 71.6% of total N-glycan, biantennary-type structures (GlcNAc(2)Man(3) GlcNAc(2)) 8.4%, and hybrid type structure (GlcNAc(1) Man(4)GlcNAc(2)) 3.0%, Although the complete structures of the remaining 17% N-glycans; C4, (HexNAc(3) Hex(3)HexNAc(2): 3.0%), D2 (HexNAc(2)Hex(5)HexNAc(2): 4.5%), and D3 (HexNAc(3)Hex(4)HexNAc(2): 9.5%) are still obscure so far, ESI-MS analysis, exoglycosidase digestions by two kinds of beta -N-acetylglucosaminidase, and WGA blotting suggested that these N-glycans might bear a beta1-4 linkage N-acetylglucosaminyl residue.