Chymotrypsin is an enzyme that catalyzes the hydrolytic cleavage of the peptide

Question

Chymotrypsin is an enzyme that catalyzes the hydrolytic cleavage of the peptide bond after large hydrophobic residues.
a) Draw the amino acids involved in the catalytic triad of chymotrypsin. Which of these amino acids acts as a strong nucleophile in the very beginning of the catalytic reaction? Is this amino acid usually capable of being a nucleophile? Why or why not? What happens to this amino acid’s pKa in this catalytic triad – does it increase or decrease, and why?
b) You change the pH of your solution of chymotrypsin and see the following relationship:

Why would this be? Consider the catalytic triad; which step of the reaction would be most affected by this pH change?

c) What is the oxyanion hole? Draw the parts of the enzymatic reaction that the oxyanion hole is involved in.

d) What is the function of the hydrophobic pocket? What amino acids would you expect to find in that pocket (the enzyme’s amino acid’s – not the amino acids of the protein being cleaved)? If a residue in the hydrophobic pocket was mutated to a Glu (and the protein did not change its tertiary structure), what would you expect to happen to the specificity of the enzyme?

Explanation / Answer

a)

2.

3.

d.

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