An isolated oral bacterial polypeptide having amidolytic activity for
cleavage of denatured polypeptides and nondenatured serpin polypeptides
and particularly a human .alpha..sub.1 -proteinase inhibitor polypeptide
is provided. The mature polypeptide of the invention has a molecular
weight of about 70 kD to about 80 kD. Also provided is an isolated nucleic
acid sequence encoding the oral bacterial polypeptide of the invention,
methods for identifying inhibitors of the polypeptide and compositions
such as immunogenic compositions and inhibitor compositions.
