Wasp venom uniquely contains wasp kinin that exhibit kinin-like activity. Other blood proteins act as enzymes, complement components, protease inhibitors or kinin precursors. The excess plasmin also activates the complement and kinin systems. It can process kininogen into kinin, and cleave immunoglobulins. The kinin B and B receptors belong to G protein coupled receptor (GPCR) family. A kinin is any of various structurally related polypeptides, such as bradykinin and kallidin.