Inga vera trypsin inhibitor interferes in the proteolytic activity and nutritional physiology of Ephestia kuehniella larvae

Plant peptidase inhibitors provide plants with a defense strategy to inhibit insect digestive enzymes and have been studied as an alternative strategy for pest control as they interfere in normal insect physiology. We evaluated the effects of ingestion of the trypsin inhibitor from Inga vera Willd. (Fabaceae) seeds on the nutritional and digestive physiology of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) larvae. Inga vera trypsin inhibitor (IVTI) reduced the efficiency of the conversion of ingested and digested food in these larvae and increased the metabolic cost, causing an anti‐nutritional effect. In both short‐ and long‐term bioassays, the ingestion of IVTI inactivated most of the insect's trypsin activity, but increased chymotrypsin activity as a compensatory response by the insect; however, protein digestion continued to be partially blocked. Consequently, chymotrypsin‐like enzymes, which were over‐produced in the gut, were excreted more into the frass of IVTI‐fed larvae. As such, the resistance of IVTI to hydrolysis by insect midgut proteases resulted in detrimental effects to larvae. These data provide support for the use of IVTI as a biotechnological tool for pest control.