抄録
An allergenic pentasaccharitol, Gp-1β-b6, was isolated as a minimum structural unit responsible for the allergic reaction in skin of patients with sea squirt allergy from a saccharitol fraction, Gp-1β-b, that had been liberated by β-elimination from a glycopep-tide in a Pronase digest of a sea squirt antigen, Gi-rep. Methylation/GC-MS and FAB-MS analyses indicated the sugar sequence of Gp-1β-b6 to be GalNAc1→2Fucl→(GalNAc1→) 3, 4G1cNAc1→3GalNAc-ol. To analyze the structure in more detail, Gp-1β-b6 was labeled with p-aminobenzoic acid ethyl ester (ABEE), i.e., the reducing terminal 3-O-substituted Ga1NAc-ol of the saccharitol was oxidized to 2-O-substituted L-ThrNAc with equimolar periodate, and the resultant aldehyde was labeled with ABEE by reductive amination. The ABEE-labeled Gp-1β-b6 was subjected to sequential exoglycosidase digestion with α-N-acetylhexosaminidase, α-N-acetylgalactosaminidase, and α-fucosidase, and the digests were chromatographed on an HPLC column of TSK gel Amide 80. From the results of the HPLC, methylation/GC-MS, and FAB-MS analyses of the digests of the labeled substrate, the structure of Gp-1β-b6 was determined to be GalNAcα1→2Fucα1→3(GalNAc β1→4)GlcNAcβ1→3GalNAc-ol. Enzymatic elimination of either the non-reducing terminal α-Ga1NAc or the non-reducing terminal α-Ga1NAc led to inactivation of the allergenic pentasaccharitol. Accordingly, it is possible that the allergenic saccharitol contains two disaccharide units as the allergy-specific epitopes, one GalNAcα1→2Fucα1→ and the other GlicNAcβ1→4GlcNAcβ1→.
