Concept #1: Chymotrypsin's Catalytic Mechanism

Concept #2: Acylation Phase of Chymotrypsin's Mechanism

Concept #3: Deacylation Phase of Chymotrypsin's Mechanism

Practice: How is chymotrypsin’s specificity for its substrate determined?

Practice: Chymotrypsin’s acylation phase is below. The catalytic process of __________ is illustrated by arrow # ____ and the catalytic process of _________________________ is illustrated by arrow # ____.

Concept #4: Review of Chymotrypsin's Entire Catalytic Mechanism

Practice: In the mechanism of chymotrypsin, serine-195:

Practice: Sequentially number the following steps of Chymotrypsin’s catalytic mechanism in the correct order from 1-8:

a) Released newly formed amine portion of the substrate diffuses away _______

b) His-57 deprotonates the Ser-195 hydroxyl group, generating a stronger nucleophile ______

c) Tetrahedral intermediate collapses & His-57 donates a H+ to N of scissile bond (cleaved peptide bond) ______

d) Via general-base-catalysis, His-57 deprotonates a water molecule, generating OH- ______

e) Tetrahedral intermediate collapses & His-57 donates a proton to Ser-195 (cleaving ester bond) _______

f) Released newly formed carboxylic acid portion of the substrate diffuses away & enzyme is restored _______

g) Hydroxide ion attacks the carbonyl group of the substrate, forming another tetrahedral intermediate ______

h) Nucleophilic Ser-195 attacks the carbonyl C of the substrate forming a tetrahedral intermediate______