ИСТИНА

Gliadins are widespread dietary proteins, which contain 10-30% Pro and 30-50% Gln residues. Several toxic gliadins peptides, resistant to proteolysis by human digestive enzymes cause autoimmune Celiac Disease in 1% of the susceptible human population. Search for natural enzymatic systems, capable to hydrolyze gliadins is an urgent task. Tenebrionidae insects are stored product pests and predicted hosts of such proteolytic system. Gliadins are their main food proteins; therefore, tenebrionids should possess enzymes capable to digest them. We have carried out a bioinformatic search for proline-specific peptidases (PSP) in Tenebrio molitor larval gut transcriptome and found 11 sequences homologous to human PSP. Combination of gene expression studies of the larval gut transcriptome with biochemical localization experiments allowed us to propose the digestive function for the highly expressed secreted dipeptidyl peptidase 4 (DPP 4) and prolylcarboxypeptidase (PRCP), and also for tissue localized prolidase (XPD). Previously we have shown that cysteine cathepsins (СС) are the major post-glutamine cleaving endopeptidases (PGP) in Tenebrionidae insects. We studied the effect of individual T. molitor digestive PGP – СС and PSP – DPP 4 and PRCP, and combined action of these peptidases on gliadins and suggested the hypothetical scheme of complete hydrolysis of γ- and ω-gliadins fragments with PQQPFPQ repeats. At the first stage, CС can hydrolyze the bond between two Gln residues. Resulting fragments are substrates for DPP 4, which cleaves dipeptides from their N-terminus. Remaining tripeptides can be hydrolyzed by PRCP. XPD may complete gliadins degradation, cleaving final dipeptides. Therefore, this natural complex provides complete gliadins hydrolysis and has a high potential as a possible preparation for Сeliac enzyme therapy. This work was supported by RFBR grants №17-54-61008 Egypt_a, 18-04-01221_а and RFBR-NID grant №17-34-80158 mol_ev_a.