Hydrolysis of food-derived opioids by dipeptidyl peptidase IV from Lactococcus lactis spp. lactis.

Food-derived opioid peptides that are released from proteins by digestion, fermentation, or food production processes lead to several health problems. The opioids are generally resistant to hydrolyze by proteases, except the dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5) enzyme, because of proline amino acid. β-casomorphin (BCM) from milk casein, gluteomorphin (GM) from wheat gluten, and soymorphin (SM) from the soybean β-conglycinin β-subunit are natural substrates of DPPIV because of their amino acid sequences and proline location. In the present study, DPPIV from Lactococcus lactis spp. lactis was purified and characterized by mass spectrometry. Purified DPPIV was added to standard BCM, GM, and SM, and hydrolysis percentages of morphins were measured by HPLC analysis. The results indicated that DPPIV enzyme hydrolyzed food-derived opioids (from 0.1 mM to 2 mM), BCM (33.42% for 2 mM), SM (83.81% for 2 mM), and GM (45.73% for 2 mM) in vitro. Hydrolysis percentages of SM were considerably higher than the same concentrations with BCM and GM. For dietary supplements to be promising for reducing the adverse effects of food derived opioids, this must be supported by in vivo studies of DPPIV use in the human body.