- Chymotrypsin is a digestive serine endopeptidase produced by the pancreas and secreted into the small intestine in its inactive precursor form, chymotrypsinogen. It plays a key role in the breakdown of dietary proteins by catalyzing the hydrolysis of peptide bonds, with a preference for cleaving at the carboxyl side of aromatic amino acids such as phenylalanine, tyrosine, and tryptophan. This substrate specificity is determined by the enzyme’s hydrophobic S1 binding pocket, which accommodates the aromatic side chains of these amino acids.
- Activation of chymotrypsinogen occurs in the small intestine, where it is cleaved by trypsin, another pancreatic serine protease. This initial cleavage produces an active intermediate (π-chymotrypsin), which undergoes further autocatalytic cleavage to yield the fully active α-chymotrypsin form. The active enzyme consists of three polypeptide chains linked by disulfide bonds and retains the highly conserved catalytic triad of serine, histidine, and aspartate, characteristic of serine proteases.
- Functionally, chymotrypsin complements the activity of other digestive proteases such as trypsin and elastase by targeting different peptide bonds, ensuring efficient protein degradation in the intestinal lumen. It contributes significantly to the generation of smaller peptides and free amino acids that can be absorbed by the intestinal mucosa.
- In biotechnology and biochemical research, chymotrypsin is widely used for controlled proteolysis due to its defined cleavage specificity. It serves as a model enzyme for studying enzyme kinetics, catalytic mechanisms, and protein folding, and it is also used in the sequencing of proteins and peptide mapping.
- Regulation of chymotrypsin activity is crucial for preventing pancreatic autodigestion. Like other proteases, its premature activation in the pancreas can lead to pancreatitis. Thus, it is tightly regulated by its zymogen form and by endogenous inhibitors.
- In summary, chymotrypsin is a vital digestive enzyme and a model serine protease. It plays a central role in protein catabolism and has broad applications in enzymology, biotechnology, and molecular biology.
