LAUSR

Angiotensin Ι-converting enzyme (ACE) inhibitory peptide was derived from hen ovotransferrin and identified as Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr. It produced a concentration-dependent inhibition of ACE activity in vitro with an IC50 value of 102.8 μM. After hydrolysis by ACE, the product (Lys-Val-Arg-Glu-Gly-Thr) has an IC50 value of 9.1 μM that was about 11-fold lower of the parent peptide. Thus, Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr can be considered as a pro-drug. Moreover, Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr and Lys-Val-Arg-Glu-Gly-Thr were intravenously administered into spontaneously hypertensive rats (SHR) to monitor the time-course change of systolic blood pressure. We found that Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr and its hydrolyzed product produced the maximal reduction of systolic blood pressure at 40 min and 20 min after injection, respectively. This 20 min delay might be considered as the time required for conversion of prodrug into Lys-Val-Arg-Glu-Gly-Thr, the true ACE inhibitor. In conclusion, the obtained results suggest that Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr works as the pro-drug of Lys-Val-Arg-Glu-Gly-Thr to inhibit ACE activity in vivo.