SDS–PAGE (A) and activity staining (B) of CPE, TPP, ATPS and BE fractions from hepatopancreas of Pacific white shrimp. L: low-molecular-weight standard; C: crude
protease extract; T: TPP fraction (The middle phase of TPP containing CPE: t-butanol (1:0.5) and 30% (NH4)2SO4); (A) ATPS fraction containing 15% PEG1000–25% MgSO4; (B)
BE containing 25% PEG8000–10% MgSO4.