Serine protease which possesses both gelatinolytic and caseinolytic activities. Shows a preference for Arg in the P1 position. Inhibited by SERPINA5. Forms a heterodimer with SERPINA5 and SERPINE1. Activated by cleavage and secreted. Expressed in epidermal, oral and male reproductive tissues. N-glycosylated. Belongs to the peptidase S1 family. Extended N-terminus.