Comparative effects of angiotensin IV and two hemorphins on angiotensin-converting enzyme activity

The role of angiotensin IV (AngIV) in the regulation of angiotensin-converting enzyme (ACE) was studied in vitro. This study demonstrates that this active fragment appeared as a novel endogenous ACE inhibitor. Inhibitory kinetic studies revealed that AngIV acts as a purely competitive inhibitor with a K-i value of 35 muM. AngIV was found to be quite resistant to ACE hydrolysis opposite to hemorphins which are both ACE inhibitors and substrates. In order to confirm a putative role of AngIV and hemorphins in the Renin-Angiotensin system (RAS) regulation, we studied their influence on AngI conversion. We noticed that 16.7 muM of both peptides decreased more than 50% of AngI conversion to AngII in vitro. The capacity of hemorphins, particularly LVVH-7, and AngIV to inhibit ACE activity here suggests a synergistic relation between these two peptides and the regulation of RAS. (C) 2002 Elsevier Science Inc. All rights reserved.