glycob.oxfordjournals.org
Hiroki Nakagawa 1, Yoichiro Hama 2, Toshihisa Sumi 2, Su-Chen Li 3, Karol Maskos 3, Kittiwan Kalayanamitra 4, Shuji Mizumoto 5, Kazuyuki Sugahara 5, and Yu-Teh Li 6 *
1 Department of Biochemistry, Tulane University Health Sciences Center School of Medicine, New Orleans, LA 70112; Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan
2 Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan
3 Department of Biochemistry, Tulane University Health Sciences Center School of Medicine, New Orleans, LA 70112
4 Department of Biochemistry, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658-8558, Japan
5 Department of Biochemistry, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658-8558, Japan; Lab. of Proteoglycan Signaling and Therapeutics, Faculty of Advanced Life Science, Hokkaido University, Frontier Research Center for Post-Genomic Science and Technology, Kita 21-jo, Nishi 11-choume, Kita-ku, Sapporo 001-0021, Japan
6 Department of Biochemistry, Tulane University Health Sciences Center School of Medicine, New Orleans, LA 70112, USA
* To whom correspondence should be addressed.
Yu-Teh Li, E-mail: yli1@tulane.edu
Abstract
Despite their wide occurrence, proteoglycans (PGs) have never been isolated from the saliva of higher animals. We found that the collocalia glycoproteins isolated from edible bird’s nests (the dried forms of regurgitated saliva of male collocalia swiftlets) were rich in a PG containing non-sulfated chondroitin glycosaminoglycans (GAGs). We have devised a method to isolate a PG from the water extract of the white nest built by Aerodramus fuciphagus (white nest swiftlets) with a yield of 2 mg PG/g nest. This PG contained 83% of carbohydrates of which 79% was GalNAc and GlcUA in an equimolar ratio. By using chondroitin AC lyase the structure of GAGs in this PG was established to be chondroitin (4GlcUA1 3GalNAc1 )n chains. The average molecular mass of the chondroitin chain was estimated to be 49 kDa by gel filtration. We have isolated a linkage region hexasaccharide, HexUA1 3GalNAc1 4GlcUA1 3Gal1 3Gal1 4Xyl, from this PG by chondroitinase ABC digestion to show that the GAGs in this PG are also linked to the core protein through the common tetrasaccharide linker, GlcUA1 3Gal1 3Gal1 4Xyl, found in various PGs. As water was not effective in extracting uronic acid-containing glycoconjugates from the black nest built by black nest swiftlets (A. maximus), we used 4 M guanidium chloride, and anion-exchange chromatography in the presence of urea to extract and isolate about 30 mg of a chondroitin PG preparation from 10 g of the desialylated black nest. As the biological significance of chondroitin is still not well understood, bird’s nest should become a convenient source for preparing this unique GAG to study its biological functions.
Keywords: chondroitin; proteoglycan; glycosaminoglycan; bird’s nest; saliva.
