Bradykinin potentiator B, secreted by the viper venom gland, inhibits the activity of the angiotensin-converting enzyme (ACE) by a preferential interaction with its C-domain. Bradykinin potentiator B also enhances the hypotensive effects of bradykinin by inhibiting the peptidases that inactivate it. Bradykinin potentiator B peptide inhibits the rabbit lung ACE with an IC50 of 1.1 uM. Bradykinin potentiator B is a 11-aa peptide corresponding to aa85-95 of bradykinin-potentiating and C-type natriuretic peptides precursor sequence.Viper: pGlu-Gly-Leu-Pro-Pro-Arg-Pro-Lys-Ile-Pro-Pro-OH or pEGLPPRPKIPP-OH