Thiol protease. Strongly inhibited by the cysteine protease inhibitor E-64. Not inhibited by the serine protease inhibitor PMSF, the aspartic protease inhibitor pepstatin A, or by the metal ion chelator 1,10-phenanthroline. Optimum pH for casein is 7.6 and philibertain g 1 retains more than 80% of maximum activity between pH 6.7 and pH 8.7, and 50% of maximum activity between pH 6.1 and pH 9.8. Optimum pH for PFLNA is 6.2-7.2 and philibertain g I retains more than 80% of maximum activity between pH 5.8 and pH 7.8, and 50% of maximum activity between pH 5.2 and pH 8.6. Monomer. Belongs to the peptidase C1 family.