Final answer:
The catalytic triad of chymotrypsin consists of three key amino acids: histidine, serine, and aspartate. This triad is crucial for the hydrolysis of peptide bonds next to aromatic amino acids in protein substrates. Chymotrypsinogen is converted to active chymotrypsin in the small intestine by trypsin.
Step-by-step explanation:
The Catalytic Triad of Chymotrypsin
The catalytic triad of chymotrypsin, a serine protease, is a group of three amino acids that are essential for its enzymatic activity. These three amino acids – histidine (His), serine (Ser), and aspartate (Asp) – work synergistically to catalyze the hydrolysis of peptide bonds. Histidine serves as a base that accepts a proton from the serine, enhancing its nucleophilicity. Aspartate helps stabilize the positive charge on the histidine imidazole ring that occurs during this process. The serine's oxygen atom attacks the carbonyl carbon of the peptide bond in the protein substrate, leading to cleavage. Chymotrypsin is specific for peptide bonds adjacent to the carboxyl group of aromatic amino acids like phenylalanine, tyrosine, and tryptophan, thus facilitating protein digestion.
Chymotrypsin is secreted by the pancreas as an inactive form known as chymotrypsinogen. This zymogen is activated in the small intestine by trypsin, another protease, during protein digestion. This process ensures that the protease activity is controlled and only occurs where it is needed, preventing potential damage to the pancreas or other tissues.
In general, catalytic reactions in enzymes like chymotrypsin involve general acid-base catalysis, where amino acids within the active site of the enzyme can act as proton donors or acceptors to facilitate the chemical reaction. In the case of chymotrypsin, the catalytic triad performs this role to effectively catalyze the cleavage of peptide bonds in proteins.