Immunoglobulin A1 Protease Activity in Gemella haemolysans

The purpose of this study was to determine the occurrence and nature of immunoglobulin A1 (IgA1) protease activity in members of the genus Gemella and related taxa. Among a total of 22 Gemella strains belonging to the four species Gemella haemolysans, Gemella morbillorum, Gemella sanguinis, and Gemella bergeriae and four reference strains of the species Helcococcus kunzii, Facklamia hominis, and Globicatella sanguinis, IgA1 protease activity was an exclusive character of all nine isolates of G. haemolysans. The IgA1 protease of G. haemolysans appears to be a metallo-type IgA1 protease that cleaves the Pro(227)-Thr(228) peptide bond in the hinge region of the α1 chain like that of several Streptococcus species. Phenotypic characterization of the isolates demonstrates that screening for IgA1 protease activity provides a valuable means for species differentiation in this group of bacteria.