Question

protease action of Chymotrypsin as a model of a specific type of enzyme mechanism. Answer the following questions about chymotrypsin.

List the residues involved in the “catalytic triad”:

What is the specificity of Chymotrypsin? (where does it cut)

What type of protease is Chymotrypsin?

What type of general enzyme mechanism is used by chymotrypsin?

What is the oxyanion hole used for?

Briefly outline the steps in catalysis for the enzyme.

Answer 1

Residues involved in the "Catalytic triad " ; Serine, histidine and aspartic acid.

Specificity of chymotrypsin means it cuts specifically at carboxyl terminal of aromatic amino acid and methionine

Chymotrypsin is Serine protease.

Enzyme mechanism used by chymotrypsin-

Chymotrypsin cleaves peptide bonds by attacking the unreactie carbonyl group with a powerful nuceophile, the ser residue located in active site of enzyme, forming an enzyme-substrate intermediate. The highly reactive seryl residue, Ser¹⁹⁵, participates in a charge relay network with His⁵⁷ and Asp¹⁰². The -NH group of this imidazole ring is, in turn, hydrogen bonded to the carboxylate group of Asp¹⁰². The catalytic triad act as a Charge relay system. This enzyme finally catalyzes the hydrolysis of peptide bonds of protein especially at carboxyl terminal of aromatic amino acid.