Digestive aspartic proteases from sábalo (Prochilodus lineatus): Characterization and application for collagen extraction.

Acid proteases from sábalo stomach mucosa were recovered using salting-out procedure. This single step produced an enzyme extract purified 1.8-fold over the crude extract with a recovery of 45.1% of its initial proteolytic activity. Sábalo proteases exhibited the highest activity at 45 °C-pH 2.0, showed pH stability between 2.0 and 5.0 and retained more than 70% of its activity after incubation at pH 7.0 for 2 h. Fish extract was unstable at temperatures greater than 45 °C. Its activity was inhibited by pepstatin A but not by PMSF, while EDTA and SDS showed partial inhibitory effects. Presence of CaCl2 and MgCl2 increased the proteolytic activity, while increasing concentrations of NaCl strongly decreased it. In addition, compared to the acid extraction method, the use of sábalo enzymatic extract increased 1.7 times the yield of collagen extraction.