Cysteine protease isoforms obtained from the midgut of 5th instar Anticarsia gemmatalis (Hübner, 1818) larvae were characterized. The soluble enzyme isoform was called Soluble Fraction and cell membrane-bound enzyme isoform, the Insoluble Fraction. The highest activities were observed at pH 3.6 and 45° C for the Soluble Fraction and pH 4.6 and 50° C for the Insoluble Fraction. Analyzing the effect of chemical modifiers, the Soluble Fraction was shown to be insensitive to aprotinin and E-64, although its activity was increased by the addition of EDTA and slightly inhibited by the addition of Ca2+, showing to be enzymes independent of metal ions to its activity. The Insoluble Fraction was also insensitive to aprotinin, but its activity was partially inhibited by E-64. The addition of EDTA reduced the activity values, demonstrating the need for metal ions for the activity of these enzymes, but they are not calcium-dependent enzymes, since their activity was reduced with the addition of this ion. The values of K M app and Vmax app were, respectively, 0.6398 mM and 42.556 nM s-1 for Soluble Fraction and 0.0413 mM and 10.854 nM s-1 for Insoluble Fraction. These results provide evidence for the presence of soluble and cell membrane-bound cysteine proteases in the gut of A. gemmatalis larvae. The knowledge and characterization of the major classes of proteases produced by the digestive tract of the soybean caterpillar, as well as the interaction of these enzymes with protease inhibitors, have a major implication for soybeans breeding programs.
Digestive proteases; Lepidoptera; pest control; protease inhibition
