Giant Amazonian fish pirarucu (Arapaima gigas): Its viscera as a source of thermostable trypsin

摘要

A trypsin was purified from pyloric caeca of pirarucu (Arapaima gigas). The effect of metal ions and protease inhibitors on its activity and its physicochemical and kinetic properties, as well its N-terminal sequence, were determined. A single band (28.0 kDa) was observed by SDS-PAGE. Optimum pH and tem perature were 9.0 and 65 ℃, respectively. The enzyme was stable after incubation for 30 min in a wide pH range (6.0-11.5) and at 55 ℃. The kinetic parameters K_m, k_mt and k_(car)/K_m were 0.47 ± 0.042 mM, 1.33 s~(-1) and 2.82 s~(-1) mM~(-1), respectively, using BApNA as substrate. This activity was shown to be very sensitive to some metal ions, such as Fe~(2+), Hg~(2+), Zn~(2+), Al~(2+), Pb~(2+), and was highly inhibited by trypsin inhibitors. The trypsin N-terminal sequence IVGGYECPRNSVPYQ was found. The features of this alkaline peptidase sug gest that it may have potential for industrial applications (e.g. food and detergent industries).