Digestive proteinases of Yellow mealworm (Tenebrio molitor) larvae:: Purification and characterization of a trypsin-like proteinase

A new trypsin-like proteinase was purified to homogeneity from the posterior midgut of Tenebrio molitor larvae by ion-exchange chromatography on DEAE-Sephadex A-50 and gel filtration on Superdex-75. The isolated enzyme had molecular mass of 25.5 kD and pI 7.4. The enzyme was also characterized by temperature optimum at 55 degrees C, pH optimum at 8.5, and K value of 0.04 mM (for hydrolysis of Bz-Arg-pNA). According to inhibitor analysis the enzyme is a trypsin-like serine proteinase stable within the pH range of 5.0-9.5. The enzyme hydrolyzes peptide bonds formed by Arg or Lys residues in the PI position with a preference for relatively long peptide substrates. The N-terminal amino acid sequence, IVGGSSI-SISSVPXQIXLQY, shares 50-72% identity with other insect trypsin-like proteinases, and 44-50% identity to mammalian trypsins. The isolated enzyme is sensitive to inhibition by plant proteinase inhibitors and it can serve as a suitable target for control of digestion in this stored product pest.