Two　novel　bradykinin-related　peptides　(Ala3,Thr6)-bradykinin　and　(Val1,Thr3,Thr6)-bradykinin,　were　identified　by　a　systematic　sequencing　study　of　peptides　in　the　defensive　skin　secretion　of　the　yellow-bellied　toad,　Bombina　variegata　.　These　peptides　are　the　first　amphibian　skin　bradykinins　to　exhibit　amino　acid　substitutions　at　the　Pro3　position　of　the　bradykinin　nonapeptide.　Previously　reported　bradykinins　from　other　Bombina　species　were　not　detected.　Respective　precursor　cDNAs,　designated　BVK-1　and　BVK-2,　respectively,　were　cloned　from　a　skin　library　by　3＇-　and　5＇-RACE　reactions.　BVK-1　contained　an　open-reading　frame　of　97　amino　acids　encoding　a　single　copy　of　(Ala3,Thr6)-bradykinin　and　similarly,　the　open-reading　frame　of　BVK-2　consisted　of　96　amino　acids　encoding　a　single　copy　of　(Val1,Thr3,Thr6)-bradykinin.　Synthetic　replicates　of　each　novel　bradykinin　were　found　to　be　active　on　mammalian　arterial　and　small　intestinal　smooth　muscle　preparations.　The　structural　diversity　of　bradykinins　in　amphibian　defensive　skin　secretions　may　be　related　to　defence　against　specific　predators.