Streptococcus anginosus is considered to be implicated in the etiology of oral infectious diseases as well as abscess formation in various body sites. We investigated the production and the enzymatic properties of PTP of S. anginosus NCTC 10713. This enzyme was found only in cell extract and active on tripeptide substrates containing proline residue at P1 position, particularly H−Ala−Ala−Pro−p−nitroanilide. The enzyme was produced by all 8 species of tested streptococci, indicating occurrence of this enzyme is rather ubiquitous within streptococci. This PTP was purified to homogeneity from the cell extract by the procedures including ammonium sulfate precipitation, chromatography, gel filtration and electrophoresis. The enzyme was inhibited by serine enzyme inhibitors and chelating reagents, indicating this PTP is a serine metalloenzyme with a molecular mass of 66 kDa. The enzyme was active against H−Ala−Ala−Pro−p−nitroanilide and H−Ala−Phe−Pro−p−nitroanilide in neutral pH solutions. The activity was completely lost by heating at 50°C for 10min
