Molecular cloning and biochemical characterisation of proteases from Staphylococcus epidermidis

We report the complete coding sequence and the partial amino acid sequence (determined by chemical sequencing) of Staphylococcus epidermidis extracell ular cysteine (Ecp) and serine (Esp) proteases. The first enzyme shows an e xtended sequence similarity to Staphylococcus aureus cysteine protease (sta phopain) and the second one resembles the serine protease produced by that species. The region directly upstream of the sequence coding for the mature protein in both enzymes displays significant homology to the profragments encoded by sspB and sspA, respectively, thus suggesting that the characteri sed enzymes may also be produced as proproteins. Furthermore, we report som e biological properties of the cysteine protease, contributing to a better understanding of its role as a possible virulence factor. The proteolytic a ctivity of this enzyme was rapidly and efficiently inhibited by human alpha -2-macroglobulin; however, human kininogen as well as cystatins (A, C and D) were not inhibitory. Moreover, the protease was capable of inactivating, by limited proteolysis, both a-l-antitrypsin and HMW-kininogen, but neithe r alpha -1-antichymotrypsin nor antithrombin Ill.