Chymotrypsin: Uses & Functions

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

The body uses several enzymes to digest food. One of these enzymes, chymotrypsin, is for digesting proteins. We will learn about this and other uses of chymotrypsin outside of digestion.

Digesting Proteins

When you eat fried chicken, or some scrambled eggs, you are consuming a lot of protein. The body can use this protein to build muscles and produce energy. First, the protein needs to get absorbed into the system, but the digestive tract isn't able to absorb large molecules - and proteins are huge! The protein needs to be broken down into individual amino acids, and then those individual amino acids can be absorbed.

There are several enzymes and methods that the body uses to break down proteins. The process starts in the stomach, with the stomach acid opening up the protein into a long chain so that each amino acid is more easily accessible. Once the protein enters the duodenum (where the stomach meets the small intestine), the pancreas releases several enzymes that are used to break apart the protein chain into individual amino acids. One of these enzymes is chymotrypsinogen, the inactive form of chymotrypsin.

Once chymotrypsinogen is in the small intestine, another enzyme, trypsin, can activate chymotrypsinogen by performing a hydrolytic cleavage of the enzyme. At this point chymotrypsin, the enzyme that can break down proteins, is active.

After all the protein has been broken down, chymotrypsin needs to be deactivated, otherwise it would begin digesting the proteins in the small intestine wall - destroying your small intestine!

Chymotrypsin Enzymatic Activity

There are several different enzymes that help break down proteins into amino acids. Each one has specific amino acid residues that it acts on. Chymotrypsin can act on the aromatic amino acids (tyrosine, phenylalanine, and tryptophan). This means that at points on the protein chain containing a tyrosine, phenylalanine, or tryptophan residue, chymotrypsin can come in and cut the protein at that point.

Let's take a look at the following protein strand:

Amino acid chain

We can see that there is a tyrosine at the 5th residue, which is one of the amino acid residues that chymotrypsin can act on:

Tyrosine is circled in red
Tyrosine circled on chain

Chymotrypsin can cleave the protein at this point, at the c-terminal, creating two protein chains:

Two chains

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