Novel angiotensin-I-converting enzyme inhibitory peptides derived from recombinant human alpha(s1)-casein expressed in Escherichia coli

Recombinant human alpha(s1)-casein expressed in Escherichia coli was purifi ed and digested with trypsin in an attempt to find peptides with angiotensi n-I-converting enzyme (BCE) inhibitory activity. Three novel ACE inhibitory peptides, A-II; B-II and C, were isolated and their amino acid sequences i dentified as Tyr-Pro-Glu-Arg (residues 8-11), Tyr-Tyr-Pro-Gln-Ile-Met-Gln-T yr (residues 136-143) and Bsn-Asn-Val-Met-Leu-Gln-Trp (residues 164-170) re spectively. ACE inhibitory activities were measured for the corresponding s ynthetic peptides, and the ACE IC50 (the amount of peptide causing 50% inhi bition of ACE activity) values of A-II, B-II and C estimated to be 132.5, 2 4.8 and 41.0 mu mol/l respectively. Peptides A-II and C mere resistant to f urther digestion by pepsin, whereas peptide B-II was hydrolysed. All three peptides were resistant to digestion by chymotrypsin. These ACE inhibitory peptides map prove useful for oral administration in the treatment of hyper tension.