Characterization of the recombinant PepX peptidase from Lactobacillus fermentum and its effect on gliadin protein hydrolysis in vitro

Wheat, one of the leading human food staples, contains proteins called glutens resistant to digestion. 1 to 2% of the world population is allergic to gluten in terms of an autoimmune disorder called celiac disease and suffers irreversible intestinal tissue damage. Using microbial enzymes to break down gluten peptides is one of the ways for controlling celiac disease. Probiotics are safe for human consumption bacteria; some include x-prolyl dipeptidyl peptidase, which may breakdown these peptides. On skim milk agar, the proteolytic activity of many LABs was studied. The sequence encoding PepX of Lactobacillus fermentum 6b isolated from dairy products was cloned in pET28a, and Escherichia coli BL21 was selected as the host. PepX activity against z-Gly-Pro- p NA was measured by spectrophotometry at 410 nm. The wheat flour was treated with recombinant E. coli BL21 and other strains, and the extracted fractions of gliadins were analyzed using SDS-PAGE with a 10–15% acrylamide gradient. The qualitative proteolytic activity of L. fermentum 6b isolate was significantly higher than other LABs in skim milk agar. The activity of the recombinant PepX showed an increase compared to other lactobacilli, and its apparent K m was 3.31 µM. SDS-PAGE analysis demonstrated a remarkable reduction in gliadin peptides after treatment with the recombinant PepX. It seems that the recombinant PepX, as a probiotic metabolite, can be an option to control gluten sensitivity by enzyme therapy and its ability to degrade gliadins.