We demonstrated previously that chondroitin sulfate E (ChS-E) binds to type V collagen (Munakata, H., Takagaki, K., Majima, M., and Endo, M. (1999) Glycobiology 9, 1023-1027). In this study, we investigated the structure and binding of ChS-E oligosaccharides. Eleven oligosaccharides were isolated from ChS-E by gel filtration chromatography and anion-exchange high performance liquid chromatography after hydrolysis with testicular hyaluronidase. Separately, seven oligosaccharides were custom synthesized using the transglycosylation reaction of testicular hyaluronidase. Structural analysis was performed by enzymatic digestions in conjunction with high performance liquid chromatography and mass spectrometry. This library of 18 oligosaccharides was used as a source of model molecules to clarify the structural requirements for binding to type V collagen. Binding was analyzed by a biosensor based on surface plasmon resonance. The results indicated that to bind to type V collagen the oligosaccharides must have the following carbohydrate structures: 1) octasaccharide or larger in size; 2) a continuous sequence of three GlcA␤1-3GalNAc(4S,6S) units; 3) a GlcA␤1-3GalNAc(4S,6S) unit, GlcA␤1-3GalNAc(4S) unit or GlcA␤1-3GalNAc(6S) unit at the reducing terminal; 4) a GlcA␤1-3GalNAc(4S,6S) unit at the nonreducing terminal. It is likely that these characteristic oligosaccharide sequences play key roles in cell adhesion and extracellular matrix assembly.Proteoglycan exists in tissues of many mammalian species and is widely distributed in the cell surface and extracellular matrix. It is known that its carbohydrate chain, chondroitin sulfate (ChS), 1 has various important biological activities in areas such as cell migration, recognition, and morphogenesis (1-5). Recently, greater attention has been directed toward the functions of ChS in the brain, optic nerves, and chondrocytes (6 -8). ChS has many types of structural domains that are known to participate in specific physiological functions. However, the relationship between the biological function and structure of ChS domains is not yet fully understood. Recently, we used a surface plasmon resonance (SPR) biosensor to investigate the interaction of glycosaminoglycans (GAGs) with collagens and glycoproteins from the extracellular matrix (9). It was found that chondroitin sulfate E (ChS-E) has specific affinity for type V collagen, and that a novel characteristic sequence included in ChS-E is probably involved in binding to type V collagen. ChS-E from squid cartilage consists mainly of the disaccharide units GlcA␤1-3GalNAc(4S,6S), GlcA␤1-3GalNAc(4S), GlcA␤1-3GalNAc(6S), and GlcA␤1-3GalNAc, where 4S and 6S represent 4-O-and 6-O-sulfate, respectively (10, 11). Thus, since ChS-E has a variety of structures, it is likely that some specific feature of its structure is necessary for binding to type V collagen. However, the structural features within ChS-E that bind to type V collagen remain unclear.In the present work, we have prepared various oligosaccharides by testicular hyaluronidase...

We previously found that endo-␤-xylosidase from Patinopecten is an endo-type glycosidase that cleaves the xylosyl serine linkage between a glycosaminoglycan chain and its core protein (Takagaki, K., Kon, A., Kawasaki, H., Nakamura, T., Tamura, S., and Endo, M. (1990) J. Biol. Chem. 265, 854 -860). Screening for endo-␤-xylosidase activity in several cellulases detected this activity in the enzymes from Aspergillus niger, Penicillium funiculosum, Trichoderma reesei, Trichoderma viride, and Irpex lacteus. The cellulase derived from A. niger was purified, and its molecular weight was determined to be 26,000 by SDS-PAGE. Examination of the specificity of the cellulase revealed that 1) the enzyme acts on the linkage region (xylosyl serine) between a core peptide and a glycosaminoglycan chain; 2) enzymatic activity is greater with shorter glycosaminoglycan chains; 3) the enzyme readily hydrolyzes the linkage in glycosaminoglycan peptides, but intact proteoglycan is cleaved only slowly; and 4) the activity is unaffected by the glycosaminoglycan component (chondroitin sulfate, dermatan sulfate, and heparan sulfate). Judging from these enzymatic characteristics, this cellulase is different from the endo-␤-xylosidase of Patinopecten. We believe that this cellulase will become a useful tool in the further development of glycotechnology, because, like the endo-␤-xylosidase of Patinopecten, it enables the release of intact glycosaminoglycans from glycosaminoglycan peptides.

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