What is the Difference Between Trypsin and Chymotrypsin?

Trypsin and chymotrypsin are both serine proteases with high sequence and structural similarities, but they have different substrate specificities and function in the body. Here are the main differences between these two enzymes:

1. Substrate Specificity: Trypsin hydrolyzes peptide bonds at the C-terminal side of basic amino acids such as lysine and arginine. In contrast, chymotrypsin attacks the C-terminal side of aromatic amino acids like phenylalanine, tryptophan, and tyrosine. This difference in substrate selectivity is the main distinction between the two enzymes.
2. Activation: The inactive form of trypsin, trypsinogen, is activated by enterokinase, while chymotrypsinogen is activated by trypsin.
3. Loop Motion and Dynamic Properties: Different dynamic properties have been observed in the two loops of trypsin and chymotrypsin. When the two loops in trypsin were changed into chymotrypsin loops, the hybrid protein shows chymotrypsin-like cooperativity, suggesting that chymotrypsin-like motions are important to the specificity of chymotrypsin.
4. Differences in Residues: An important difference between trypsin and chymotrypsin is that residue 189 is a negatively charged Asp in trypsin and a polar Ser in chymotrypsin. This residue lies at the bottom of the S1 binding pocket and determines different S1 pocket chemical properties.

In summary, while trypsin and chymotrypsin share similarities in structure and function, they have distinct substrate specificities, activation mechanisms, loop motion properties, and residue differences. These differences contribute to their unique roles in protein hydrolysis and digestion.

Comparative Table: Trypsin vs Chymotrypsin

Trypsin and chymotrypsin are both digestive enzymes that hydrolyze proteins into amino acids during the digestion process. They share similar structures and functions, but there are some differences between these two enzymes. Here is a table summarizing the differences between trypsin and chymotrypsin:

These differences in specificity and activation contribute to the distinct roles of trypsin and chymotrypsin in protein digestion and absorption in the body.