A BRADYKININ-POTENTIATING PEPTIDE (PEPTIDE K(12)) ISOLATED FROM THE VENOM OF EGYPTIAN SCORPION BUTHUS-OCCITANUS

A nontoxic peptide with bradykinin-potentiating activity was isolated from the dialyzed venom of the scorpion Buthus occitanus by reverse-ph ase high performance liquid chromatography (RP-HPLC). The pharmacologi cal activity of the peptide was bioassayed by its ability to potentiat e added bradykinin (BK) on the isolated guinea pig ileum as well as th e isolated rat uterus for contraction. Moreover, the peptide potentiat es in vivo the depressor effect of BK on arterial blood pressure in th e normotensive anesthetized rat. Chemical characterization of the pept ide was also performed. The amino acid composition of the peptide show ed 21 amino acid residues per molecule including three proline residue s. The amino acid sequence of the purified peptide was confirmed by ma ss spectrometry. Either N- or C-terminal ends were free. The sequence does not show a homology with bradykinin-potentiating peptides isolate d from either scorpion or snake venoms. Furthermore, we did not find a significant sequence homology between the sequence of the isolated pe ptide and any of proteins or peptides in GenPro or NEW data banks. The peptide also inhibited angiotensin-converting enzyme (ACE), and could not serve as substrate for the enzyme. It could be concluded that the mechanism of bradykinin-potentiating peptide (BPP) activity may be du e to ACE inhibition.