J. Biochem, 1990, Vol. 108, No. 1 47-52
© 1990 Japanese Biochemical Society
research-article |
Structure of an Allergenic Pentasaccharitol, Gp-1ß-b6, Isolated from a Sea Squirt Antigen, Gi-rep, as a Minimum Structural Unit Responsible for Its Allergenicity
*Department of Fermentation Technology, Faculty of Engineering, Hiroshima University Higashi-Hiroshima, Hiroshima 724
**Department of Biotechnology, Faculty of Engineering, Fukuyama University Fukuyama, Hiroshima 729-02
***Institute for Protein Research, Osaka University Suita, Osaka 564
An allergenic pentasaccharitol, Gp-1ß-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-1ß-b, that had been liberated by ß-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-1ß-b6 to be GalNAcl
2Fucl
(GalNAcl
) 3,4GlcNAcl
3GalNAc-ol. To analyze the structure in more detail, Gp-1ß-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-1ß-b6 was subjected to sequential exoglycosidase digestion with ß-N-acetylhexosaminidase,
-N-acetylgalactosaminidase, and
-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-1ß-b6 was determined to be GalNAc
1
2Fuc
1
3(GalNAcß1
4)GlcNAcß1
3GalNAc-ol. Enzymatic elimination of either the non-reducing terminal ß-GalNAc or the non-reducing terminal
-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
1
2Fuc
1
and the other GlcNAcß1
4GlcNAcß1
.
1This work was supported in part by Grants-in-Aid for Scientific Research (Nos. 59124001 and 60560096) from the Ministry of Education, Science, and Culture of Japan.