The effects of Enterolobium contortisiliquum serine protease inhibitor on the survival of the termite Nasutitermes corniger, and its use as affinity adsorbent to purify termite proteases

BACKGROUND: Termites are one of the main wood destroying insects. Nasutitermes corniger (Isoptera: Termitidae), can invade and attack urban wooden environments used in the structures of buildings. The use of synthetic pesticides is the traditional method used to prevent termite attack; however, these compounds generally cause harm to the environment. This paper describes the insecticidal activity of Enterolobium contortisiliquum protease inhibitor (EcTI) on Nasutitermes corniger workers and soldiers. RESULTS: EcTI induced mortality in Nasutitermes corniger workers (LC50 0.242 mg mL(-1) at 6 days of exposure). Gut extracts from workers and soldiers showed protease activity on the H-D-Pro-Phe-Arg-pNan substrate. EcTI inhibited gut proteases in N. corniger at nM concentrations in vitro. The inhibitory activity towards termite enzymes was stable within the range of 25-65 degrees C. The inhibitor's unordered structure showed a high content of beta-sheets; its secondary structure and the thermal denaturation monitored by CD showed a two-state transition and melting temperature (T-m) of approximately 73 degrees C. CONCLUSION: Our results contribute to the understanding of Nasutitermes corniger complexity and provide newclues to achieve a better comprehension of themolecular mechanism of action of insecticides to this pest. (c) 2018 Society of Chemical Industry