Enzymes – Section 1

6. The proteolysis rate enhancement by chymotrypsin (~1010 folds) corresponds to a reduction in activation energy of about

A. 40 kJ/mol
B. 49 kJ/mol
C. 58 kJ/mol
D. 88 kJ/mol

Correct Answer: C. 58 kJ/mol

7. Which of the following is false statement with regard to comparison between Serine and HIV proteases?

A. Both use nucleophilic attack to hydrolyze the peptide bond
B. Both require water to complete the catalytic cycle
C. Both forms an acyl-enzyme intermediate
D. Both show specificity for certain amino acid sequences

Correct Answer: C. Both forms an acyl-enzyme intermediate

8. In the enzyme-catalyzed reaction shown below, what will be the effect on substances A, B, C, and D of inactivating the enzyme labeled E2?

A. A, B, C, and D will all still be produced
B. A, B, and C will still be produced, but not D
C. A and B will still be produced, but not C or D
D. A will still be produced, but not B, C, or D

Correct Answer: C. A and B will still be produced, but not C or D

9. The nucleophile in serine proteases is

A. Serine
B. water
C. both (a) and (b)
D. Asparagine

Correct Answer: C. both (a) and (b)

10. The role of Asp 102 and His 57 during trypsin catalysis is to

A. neutralize the charge on the other’s side chain
B. keep the specificity pocket open
C. function as a proton shuttle
D. clamp the substrate into the active site

Correct Answer: C. function as a proton shuttle

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