Angiotensin I-converting enzyme inhibitory oligo-tyrosine peptides synthesized by α-chymotrypsin

Oligo-tyrosine peptides with degrees of polymerization ranging from 2 to 5 could be synthesized by α-chymotrypsin-catalyzed reaction with l-tyrosine ethyl ester in aqueous media, although the peptide yield was low due to a preferential hydrolysis of the substrate. It was also confirmed that α-chymotrypsin efficiently converted tyrosine tetramer to the dimer which was resistant to the digestion. Both Tyr-Tyr and Tyr-Tyr-Tyr showed high inhibitory activity for angiotensin I-converting enzyme from rabbit lung, and their IC50 values were 34 μM and 51 μM, respectively. These two peptides exhibited a mix of competitive and noncompetitive inhibitions. Tyr-Tyr-Tyr was first recognized as an ACE inhibitor, suggesting that α-chymotrypsin could be applied to synthesis of novel potential materials for antihypertensive medicines.