has been implicated in human periodontal diseases. It expresses a number of exoglycosidase enzymes capable of hydrolysing host proteoglycan residues. As a first stage to explore the role of these enzymes in periodontal tissue damage, the gene of W83, which encodes β--acetylhexosaminidase (β-Nahase), was cloned. The gene was expressed poorly in , but increased expression was achieved by cloning the gene downstream of the tac promoter. Southern blot analysis revealed that was present as a single copy, and it was found in all the other strains tested. In contrast, sequences homologous to were not detected in either or The gene was 2331 bp long and encoded a β-Nahase enzyme of 777 amino acids with a predicted molecular mass of 87 kDa. A characteristic signal peptide for an acylated lipoprotein was present at the amino-terminus, suggesting that the mature β-Nahase is a lipoprotein. The predicted amino acid sequence of the β-Nahase shared homology with the catalytic domains of the human β-Nahase enzyme and the chitinase of , suggesting a common catalytic mechanism.


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