Klk1, or kallikrein 1, is a serine protease and an important member of the kallikrein family. It is synthesized and secreted in various tissues, including the kidneys and salivary glands. The core function of Klk1 is to catalyze the cleavage of kininogen, generating highly bioactive kinins such as bradykinin. Kinins are key inflammatory mediators and vasoactive peptides that regulate blood pressure, inflammatory responses, pain perception, and vascular permeability through their receptors. Therefore, Klk1 and its kinin system play a central role in pathological processes such as hypertension, heart failure, inflammatory diseases, and angioedema. This system is also a critical downstream pathway through which classic drugs like ACE inhibitors exert their effects, while Klk1 itself serves as a potential target for novel anti-inflammatory and analgesic drugs.