Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 8, Problem 12P
At 37 oC, the serine protease subtilisin has kcat = 50 S-1 and KM = 1.4 x 10-4 M. It is proposed that the N155 side chain contributes a hydrogen bond to the oxyanion hole of subtilisin. J. A. Wells and colleagues repotted (1986, Phil Trans. R Soc. Lond. A 317: 415-423) the following kinetic parameters for the N155T mutant of subtilisin:
kcat = 0.02 S-1 and
KM = 2 x 10-4 M.
a. Subtilisin is used in some laundry detergents to help remove protein-type stains. What unusual kind of stability does this suggest for subtilisin?
b. Subtilisin does have a problem in that it becomes inactivated by oxidation of a methionine close to the active site. Suggest a way to make a better subtilisin.
c. Is the effect of the N155T mutation what you would expect for a residue that makes up part of the oxyanion hole? How do the reported values of kcat and KM support your answer?
d. Assuming that the T 155 side chain cannot H-bond to the oxyanion intermediate, by how much (in kJ / mol) does N155 appear to stabilize the transition state at 37 oC?
e. The value you calculated in part (d) represents the strength of the H-bond between N155 and the oxyanion in the transition state. This value is higher than typical H-bonds in water. How might this observation be rationalized? Hint: Consider Equation 2.2 (Coulomb's Law).
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Chapter 8 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 8 - Prob. 1PCh. 8 - The enzyme urease catalyzes the hydrolysis of urea...Ch. 8 - An enzyme contains an active site aspartic acid...Ch. 8 - The folding and unfolding rate constants for a...Ch. 8 - In some reactions, in which a protein molecule is...Ch. 8 - Would you expect an “enzyme” designed to bind to...Ch. 8 - The initial rate for an enzyme-catalyzed reaction...Ch. 8 - a. If the total enzyme concentration in Problem 7...Ch. 8 - Prob. 9PCh. 8 - Prob. 10P
Ch. 8 - The following data describe the catalysis of...Ch. 8 - At 37 oC, the serine protease subtilisin has kcat...Ch. 8 - The accompanying figure shows three...Ch. 8 - The steady-state kinetics of an enzyme are studied...Ch. 8 - The same enzyme as in Problem 14 is studied in the...Ch. 8 - Enalapril is an anti-hypertension “pro-drug"...Ch. 8 - Initial rate data for an enzyme that obeys...Ch. 8 - Prob. 18PCh. 8 - Suggest the effects of each of the following...Ch. 8 - The inhibitory effect of an uncompetitive...Ch. 8 - Prob. 21PCh. 8 - Prob. 22PCh. 8 - Prob. 23PCh. 8 - In kinetics experiments, the hydrolysis of the...
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