Kallikrein-2 (KLK2) is a secreted serine protease that belongs to the peptidase S1 family of Kallikrein subfamily. KLK2 contains 1 peptidase S1 domain. It is highly expressed in the human prostate gland. KLK2 can cleave Met-Lys and Arg-Ser bonds in kininogen to release Lys-bradykinin, but Preferential cleavages of Arg-|-Xaa bonds in small molecule substrates. It also highly selective action to release kallidin (lysyl-bradykinin) from kininogen involves hydrolysis of Met-|-Xaa or Leu-|-Xaa. KLK2 is inhibited by serpins such as protein C inhibitor, antichymotrypsin, and plasminogen. KLK2 is considered to be a biomarker for prostate cancer.