Figure 1: Activation pathways of proenzymes and PAR-2 by trypsin. Once trypsin is activated, it is capable of activating many other digestive proenzymes. Trypsin also activates pancreatic and inflammatory cells via PAR-2. The trypsin activity in the pancreas is mainly controlled by PSTI. When trypsinogen is activated into trypsin in the pancreas, PSTI binds immediately to trypsin to prevent further activation of pancreatic enzymes. (PAR: protease activated receptors; PSTI: pancreatic secretory trypsin inhibitor)