FIGURE 2.

Two catalytic domains of ACE and biological roles of ACE in tissue fibrosis. In ACE, there are two catalytic sites. Angiotensin I exerts higher affinity for the C-terminal catalytic site of ACE. AcSDKP is a substrate for the N-terminal domain. ACE may induce tissue fibrosis by both the production of angiotensin II and the decreased level of AcSDKP. Captopril exhibits higher affinity for the N-terminal catalytic sites of ACE when compared with C-terminal catalytic sites. Furthermore, NaCl restriction on top of RAS-blockade may increase AcSDKP levels by unknown mechanisms.