Effect of β-lactoglobulin hydrolysis with thermolysin under denaturing temperatures on the release of bioactive peptides

In this study, bovine β-lactoglobulin A (β-Lg A) was hydrolysed with thermolysin under non-denaturing and heat-denaturing conditions. The peptides released during hydrolysis were identified by HPLC–MS/MS. A total of 25 peptides were identified in the hydrolysate obtained at 37 °C for 5 min. Some of these peptides survived to further proteolysis even at higher incubation temperatures. Furthermore, novel cleavage sites localised in the most buried zones of β-Lg and available for thermolysin were recognised when the incubation temperature increased in the range between 60 and 80 °C. Three new peptides, LDA, LKPTPEGD, and LQKW, appeared after 30 min hydrolysis at these incubation temperatures, but they were not identified in the 30-min hydrolysates obtained at 37 and 50 °C. Of special interest was the peptide LQKW, corresponding to the fragment f(58–61) that had been previously described as a potent angiotensin-converting enzyme-inhibitor (IC50 value of 34.7 μM).