Primary digestive cathepsins L of Tribolium castaneum larvae: proteomic identification, properties, comparison with human lysosomal cathepsin L

Authors: DVORYAKOVA, E. - Moscow State University; VINOKUROV, K. - Institute For Entomology - Czech Republic; TERESHCHENKOVA, V. - Moscow State University; DUNAEVSKY, Y. - Moscow State University; BELOZERSKY, M. - Moscow State University; Oppert, Brenda; FILIPPOVA, I. - Moscow State University; ELPIDINA, E. - Moscow State University

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Pre-print Publication
Publication Acceptance Date: 11/3/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: We are interested in the enzymes in the digestive tract of the red flour beetle because they represent an opportunity for the development of a specific and targeted pest control product. However, we also understand that the unique ability of this insect and other related beetles to effectively digest cereal proteins may also represent an opportunity to develop new treatments for people that have problems in digesting these proteins, called celiac disease. Therefore, we isolated the major digestive enzymes from the red flour beetle and studied their chemical properties. We confirmed that these enzymes are largely involved in the ability to digest cereal proteins, and therefore they not only are a primary target for insect control, they also may be useful if incorporated into products that treat celiac disease. These studies help further our understanding of using insect enzymes to design new insect control products and therapeutics for disease.

Technical Abstract: We previously described the most highly expressed enzymes from the gut of the red flour beetle, Tribolium castaneum, as cathepsins L. In the present study, two C1 family-specific cysteine cathepsin L enzymes from the larval midgut were isolated and identified using MALDI-TOF MS analysis. The isolated T. castaneum cathepsins were characterized according to their specificity against chromogenic and fluorogenic peptide substrates, and the most efficiently hydrolyzed substrate was Z-FR-pNA with Arg in the P1 subsite. The specificity of insect digestive cathepsins was compared with human lysosomal cathepsin L, the well-studied peptidase of the C1 family cathepsins. T. castaneum digestive cathepsins efficiently hydrolyzed substrates with small and uncharged amino acid residues at P1 (Ala, Gln) more than human cathepsin L. In particular, these insect digestive cathepsins cleaved with higher efficiency the analogs of immunogenic peptides of gliadins, which contribute to autoimmune celiac disease in susceptible people, and thus insect enzymes may be useful in enzymatic treatments for this disease. A bioinformatic analysis supported by the proteomic analysis of the primary structures of the isolated cathepsins was carried out, and tertiary models of zymogens were constructed. The phylogenetic analysis of coleopteran and human cathepsins from the L subfamily indicated that insect digestive cathepsins grouped separately from lysosomal cathepsins.