A protease is an enzyme that helps proteolysis: protein catabolism by hydrolysis of peptide bonds. The native Bacillus licheniformis protease belongs to the serine endopeptidase subtilisin family, which breaks the peptide bond non-specifically under alkaline conditions. The enzyme is active in aqueous solutions and in some organic solvents such as dry octane. The protease is inactivated by serine active-site inhibitors, such as phenylmethylsulfonyl fluoride (PMSF) and diisopropyl fluorophosphate.