prss 4

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.

Kallikrein-4, also known as Enamel matrix serine proteinase 1, Kallikrein-like protein 1, KLK-L1, Serine protease 17, KLK4, PRSS17, and EMSP1, is a secreted protein that belongs to the peptidase S1 family and Kallikrein subfamily. Kallikrein-4 / KLK4 is a serine protease expressed during enamel maturation, and proteolytic processing of the enamel matrix by KLK4 is critical for proper enamel formation. Kallikrein-4 / KLK4 contains one peptidase S1 domain. Kallikrein-4 / KLK4 is secreted by transition- and maturation-stage ameloblasts. KLK4 aggressively degrades the retained organic matrix following the termination of enamel protein secretion. Two proteases are secreted into the enamel matrix of developing teeth. The early protease is enamelysin (MMP-2). The late protease is kallikrein 4 (KLK4). The principal functions of MMP-2 and KLK4 in dental enamel formation are to facilitate the orderly replacement of organic matrix with mineral, generating an enamel layer that is harder, less porous, and unstained by retained enamel proteins. Defects in Kallikrein-4 / KLK4 are the cause of Amelogenesis Imperfecta Hypomaturation type 2A1 (AI2A1) which is an autosomal recessive defect of enamel formation. The disorder involves both primary and secondary dentitions.

Brain-Specific Serine Protease 4 (BSSP-4) is a serine protease that preferentially cleaves the synthetic substrate H-D-Leu-Thr-Arg-pNA compared to tosyl-Gly-Pro-Arg-pNA. BSSP-4 is expressed abundantly in the epithelial cells of the airways, including trachea, esophagus and fetal lung, but scarce in adult lung and expressed at low levels in placenta, pancreas, prostate and thyroid gland. BSSP-4 belongs to the peptidase S1 family and related to trypsin, referentially hydrolyzing substrates after arginine and lysine residues. However, BSSP-4 is less susceptible to inhibition by common trypsin inhibitors such as aprotinin, α1-antitrypsin and secretory leukocyte protease inhibitor. BSSP-4 efficiently converts pro-urokinase- type plasminogen activator to its mature, active form.