SPECIFICITY OF THE HYALURONATE LYASE OF GROUP-B STREPTOCOCCUS TOWARD UNSULFATED REGIONS OF CHONDROITIN SULFATE

The purification and properties of a hyaluronate lyase secreted by Str eptococcus agalactiae, which is believed to facilitate the invasion of host tissues by the organism, have been described previously [Pritcha rd, Lin, Willingham and Baker (1994) Arch. Biochem. Biophys. 315, 431- 436]. The specificity of the limited cleavage of chondroitin sulphate by the enzyme is the subject of this report. To simplify the task, a c hondroitin sulphate from the Swarm rat chondrosarcoma, which contains only 4-sulphated and unsulphated disaccharide repeats, was used in thi s study. Tetrasaccharides from an ovine testicular hyaluronidase diges t of the chondroitin sulphate were isolated, identified and tested as substrates of the streptococcal hyaluronate lyase. Only tetrasaccharid es with an unsulphated disaccharide at the reducing end were cleaved ( by elimination at the N-acetylgalactosaminidic bond). Thus chondroitin sulphate chains are cleaved by the action of this lyase at every unsu lphated disaccharide repeat, but release of unsaturated unsulphated di saccharides only occurs from sites where two or more sequential unsulp hated disaccharide repeats are present. Analysis of the chondrosarcoma chondroitin sulphate showed that of approximately five unsulphated di saccharide repeats per chain, two are clustered. The ability of group- B streptococcal hyaluronate lyase to cleave chondroitin sulphate may a llow the organisms to invade tissues more efficiently. The demonstrate d specific and highly limited cleavage of chondroitin sulphate by this bacterial lyase promises to be a useful tool in the determination of chondroitin sulphate structure and variability.