This protease is specific for immunoglobulin A. Cleavage of immunoglobulin A molecules at certain Pro-|-Xaa bonds in the hinge region. No small molecule substrates are known. The cleaved C-terminal fragment (autotransporter domain) is localized in the outer membrane. The signal peptide, cleaved at the inner membrane, guides the autotransporter protein to the periplasmic space. Then, insertion of the C-terminal translocator domain in the outer membrane forms a hydrophilic pore for the translocation of the passenger domain to the bacterial cell surface, with subsequent cleavage.