First insights into insecticidal activity against Aedes aegypti and partial biochemical characterization of a novel low molecular mass chymotrypsin-trypsin inhibitor purified from Lonchocarpus sericeus seeds

Abstract

BACKGROUND: Arboviroses such as dengue, Zika and chikungunya represent a serious public health issue as a consequenceof the absence of approved vaccines or specific antiviral drugs against the arboviruses that cause them. One way to preventthese diseases is by combating the vector mosquito, Aedes aegypti (Diptera), which has serine proteases in the midgut. Proteaseinhibitors are molecules that can block enzyme activity, impairing digestion and nutrition, which can lead to death. Thus, wepurified and characterized a novel chymotrypsin-trypsin inhibitor (LsCTI) from Lonchocarpus sericeus seeds and investigated itseffect upon Ae. aegypti egg hatching, larval development and digestive proteases.RESULTS: LsCTI showed a single protein band in sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE),and the molecular mass determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS) was 8870.45 Da. Kinetics analyses revealed a noncompetitive type of inhibition and low inhibition con-stant (Ki) for chymotrypsin (8.24 x 10-8M). The thermal resistance was remarkable, even at 100∘C for 180 min. The inhibitorconcentration required for 50-percent enzyme inhibition (IC50) of LsCTI was 4.7 x 10-7M for Ae. aegypti midgut larval enzymes.LsCTI did not affect egg hatchability at 0.3 mg mL-1, but caused a high larval mortality rate (77%) and delayed development(37%).CONCLUSIONS: LsCTI is a novel protease inhibitor with remarkable biochemical characteristics and is a potential tool to controlAe. aegypti development.© 2017 Society of Chemical Industry