Initial proteolysis of milk proteins and its effect on formation of ACE-inhibitory peptides during gastrointestinal proteolysis: a bioinformatic, in silico, approach

Angiotensin-I-converting enzyme (ACE)-inhibitory peptides are encrypted in milk protein sequences. They may express an antihypertensive effect if they are released by proteolysis in foods and/or during gastrointestinal digestion. A bioinformatic, in silico, approach was developed to evaluate how systematic initial proteolysis, i.e. cleavage after one specific type of amino acid (C-end) at a time in milk proteins, influence the formation of ACE-inhibitory peptides by subsequent gastrointestinal proteolysis. Computer simulation was done and a peptide QSAR model was used to estimate the combined ACE inhibition by digested proteins. Initial proteolytic cleavage at the C-end of amino acids isoleucine and proline gave, based on calculations, increased effect of ACE-inhibitory peptides after gastrointestinal proteolysis of milk proteins. Cleavage after most other amino acid residues had little or no effect. Results indicate that initial proteolysis in foods have to be specific in order to increase formation of bioavailable ACE-inhibitory peptides during gastrointestinal digestion.