The most important activator of trypsinogen is enterokinase, in special cases, when enterokinase is deficient the self-catalytic reaction of trypsin can also activate trypsinogen, sometimes acid, tissue fluid can also activate trypsinogen, to become trypsin and thus play a role. Trypsinogen enters the duodenum and is activated by enterokinase in the intestinal fluid, which converts it to trypsin. Trypsin selectively hydrolyzes arginine and lysine peptide chains, hydrolyzing natural proteins, denatured proteins, fibrous proteins, and mucins into peptides or amino acids. Enterokinase is a highly specific protease. Because of its high degree of specificity and high hydrolysis efficiency, enterokinase plays an important role in the development of genetically engineered products, such as as a tool protease in the recombination of fusion proteins to play an important role in the specific breakage of fusion proteins.