Figure 2

The nonapeptide bradykinin is digested by ACE to release Phe Arg and then Ser Pro. These products have no activity on kinin receptors. Carboxypeptidase N and/or TAFI (carboxypeptidase U) removes C-terminal Arg, leaving an octapeptide that interacts with B₁ receptors. The ACE degrades this to a pentapeptide + tripeptide.