Complex of Proline-Specific Peptidases in the Genome and Gut Transcriptomes of Tenebrionidae Insects and Their Role in Gliadin Hydrolysis

A detailed analysis of the complexes of proline-specific peptidases (PSPs) in the midgut transcriptomes of the larvae of agricultural pests Tenebrio molitor and Tribolium castaneum and in the genome of T. castaneum is presented. Analysis of the T. castaneum genome revealed 13 PSP sequences from the clans of serine and metal-dependent peptidases, of which 11 sequences were also found in the gut transcriptomes of both tenebrionid species’ larvae. Studies of the localization of PSPs, evaluation of the expression level of their genes in gut transcriptomes, and prediction of the presence of signal peptides determining secretory pathways made it possible to propose a set of peptidases that can directly participate in the hydrolysis of food proteins in the larvae guts. The discovered digestive PSPs of tenebrionids in combination with the post-glutamine cleaving cysteine cathepsins of these insects effectively hydrolyzed gliadins, which are the natural food substrates of the studied pests. Based on the data obtained, a hypothetical scheme for the complete hydrolysis of immunogenic gliadin peptides by T. molitor and T. castaneum digestive peptidases was proposed. These results show promise regarding the development of a drug based on tenebrionid digestive enzymes for the enzymatic therapy of celiac disease and gluten intolerance.