Abstract
We previously found that endo-beta-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-beta-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-beta-xylosidase of Patinopecten. We believe that this cellulase will become a useful tool in the further development of glycotechnology, because, like the endo-beta-xylosidase of Patinopecten, it enables the release of intact glycosaminoglycans from glycosaminoglycan peptides.
Highlights
Proteoglycans (PGs)1 are widely distributed in connective tissue and on the cell surface of mammalian tissues and are functional materials influencing cell growth, differentiation, and morphogenesis [1, 2]
Examination of the specificity of the cellulase revealed that 1) the enzyme acts on the linkage region 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
GAG chains are broadly divided into chondroitin sulfate (ChS), dermatan sulfate (DS), heparan sulfate (HS), heparin, hyaluronic acid, and keratan sulfate by their particular combination of repeating disaccharide units, ChS, DS, HS, and heparin are all attached to a serine residue of a core protein by the linkage region GlcA1–3Gal1–3Gal1– 4Xyl1-O-Ser [8]
Summary
We demonstrate that a fungal cellulase is able to hydrolyze the Xyl-Ser linkage between the core peptide and the GAG chain of GAG peptides. This cellulase has endo--xylosidase activity, it is different from the endo--xylosidase of Patinopecten
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