KLK1, or tissue kallikrein is a serine protease that generates Lys-bradykinin by specific proteolysis of kininogen-1. Kallikrein 1 is one of the fifteen kallikrein subfamily members located in a cluster on chromosome 19. This protein is functionally conserved in its capacity to release the vasoactive peptide, Lys-bradykinin, from low molecular weight kininogen.

the deduced 262-amino acid KLK1 protein contains a putative signal peptide, followed by a short activating peptide and the protease domain. The protease domain contains the catalytic triad of his65, asp120, and ser214. RT-PCR detected variable expression of KLK1 in most of the 35 tissues examined. Highest expression was in pancreas, salivary gland, thyroid, parotid gland, fetal and adult skin, kidney, and liver.