Structure of an allergenic pentasaccharitol, Gp-1 beta-b6, isolated from a sea squirt antigen, Gi-rep, as a minimum structural unit responsible for its allergenicity.
An allergenic pentasaccharitol, Gp-1 beta-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-1 beta-b, that had been liberated by beta-elimination from a glycopeptide in a Pronase digest of a sea squirt antigen, Gi-rep. Methylation/GC-MS and FAB-MS analyses indicated the sugar sequence of Gp-1 beta-b6 to be GalNAcl----2Fucl----(GalNAc1----) 3,4GlcNAc1----3GalNAc-ol. To analyze the structure in more detail, Gp-1 beta-b6 was labeled with p-aminobenzoic acid ethyl ester (ABEE), i.e., the reducing terminal 3-O-substituted GalNAc-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-1 beta-b6 was subjected to sequential exoglycosidase digestion with beta-N-acetylhexosaminidase, alpha-N-acetylgalactosaminidase, and alpha-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-1 beta-b6 was determined to be GalNAc alpha 1----2Fuc alpha 1----3(GalNAc beta 1----4)GlcNAc beta 1----3GalNAc-ol. Enzymatic elimination of either the non-reducing terminal beta-GalNAc or the non-reducing terminal alpha-GalNAc 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 GalNAc alpha 1----2Fuc alpha 1---- and the other GlcNAc beta 1----4GLcNAc beta 1----.
Shigeta
S
S
Department of Fermentation Technology, Faculty of Engineering, Hiroshima University.
Okamura
M
M
Tsutsumi
M
M
Ono
K
K
Ohta
M
M
Matsuura
F
F
Takao
T
T
Oka
S
S
D000485:Allergens / Q000032:analysis* / Q000276:immunology; D000818:Animals; D001566:Benzocaine; D002241:Carbohydrates / Q000032:analysis; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D006023:Glycoproteins; D006026:Glycoside Hydrolases / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008970:Molecular Weight; D009844:Oligosaccharides / Q000032:analysis* / Q000276:immunology / Q000302:isolation & purification; D013402:Sugar Alcohols / Q000032:analysis* / Q000276:immunology / Q000302:isolation & purification; D014561:Urochordata / Q000276:immunology*
D000485:Allergens; D002241:Carbohydrates; C053192:Gi-rep antigen, Sea squirt; D006023:Glycoproteins; D009844:Oligosaccharides; D013402:Sugar Alcohols; D006026:Glycoside Hydrolases; D001566:Benzocaine