Hydrolyzes semenogelin-1 thus leading to the liquefaction of the seminal coagulum. Preferential cleavage: -Tyr-|-Xaa-. Inhibited by SERPINA5. Activity is strongly inhibited by Zn2+, 100 times more abundant in semen than in serum. This inhibition is relieved by exposure to semenogelins, which are avid zinc binders. Forms a heterodimer with SERPINA5. Belongs to the peptidase S1 family. Kallikrein subfamily. Extended N-terminus. Prostate-specific antigen entry