Trypsin-3, also known as Trypsin III, brain trypsinogen, Serine protease 3 and PRSS3, is a secreted protein that belongs to the peptidase S1 family. Trypsin-3 / PRSS3 is expressed is in pancreas and brain. It contains one peptidase S1 domain. Trypsin-3 / PRSS3 can degrade intrapancreatic trypsin inhibitors that protect against CP. Genetic variants that cause higher mesotrypsin activity might increase the risk for chronic pancreatitis (CP). A sustained imbalance of pancreatic proteases and their inhibitors seems to be important for the development of CP. The trypsin inhibitor-degrading activity qualified PRSS3 as a candidate for a novel CP susceptibility gene. Trypsin-3 / PRSS3 has been implicated as a putative tumor suppressor gene due to its loss of expression, which is correlated with promoter hypermethylation, in esophageal squamous cell carcinoma and gastric adenocarcinoma.

KLK6 (kallikrein-related peptidase 6), also known as Klk7, belongs to the peptidase S1 family, Kallikrein subfamily. Kallikreins are a subgroup of serine proteases having diverse physiological functions. Growing evidence suggests that many kallikreins are implicated in carcinogenesis and some have potential as novel cancer and other disease biomarkers. KLK6 is a serine protease that exhibits a preference for Arg over Lys in the substrate P1 position and for Ser or Pro in the P2 position. Klk7 shows activity against amyloid precursor protein, myelin basic protein, gelatin, casein, and extracellular matrix proteins such as fibronectin, laminin, vitronectin, and collagen. KLK6 degrades alpha-synuclein and prevents its polymerization, indicating that KLK6 may be involved in the pathogenesis of Parkinson's disease and other synucleinopathies. Klk7 may be involved in the regulation of axon outgrowth following spinal cord injury. Tumor cells treated with a neutralizing KLK6 antibody migrate less than control cells, suggesting a role in invasion and metastasis.