MBMB 451b

Copyright 2000, E.C. Niederhoffer

Sample Problem

Subtilisin (MW 27,600) specifically hydrolyzes aromatic esters and amides. If Km and kcat for the hydrolysis of N-acetyltyrosine ethyl ester are 0.15 M and 550 s-1, respectively, provide answers to the following:

a. Given that the enzyme concentration is 0.40 mg ml-1 and the substrate concentration is 0.25 M, what is Vmax for this reaction?

Vmax = kcat[E]T

Vmax = 8.0 x 10-3 M s-1

b. Indole is a competitive inhibitor of subtilisin (KI = 0.05 M). Calculate the Vmax of the hydrolysis of the above substrate in the presence of 6.25 mM indole.

A competitive inhibitor does not change the Vmax.

c. What is the reaction velocity in the presence of 1.0 M indole?

v = 5.9 x 10-4 M s-1

 

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