Biochemistry: Concepts and Connections
1st Edition
ISBN: 9780321839923
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 8, Problem 11P
The following data describe the catalysis of cleavage of peptide bonds small peptides by the enzyme elastase.
The arrow indicates the peptide bond cleaved each case.
a. If a mixture of these three substrates was presented to elastase with the concentration of each peptide equal to 0.5 mM, which would be digested most rapidly? Which most slowly? (Assume enzyme present in excess.)
b. On basis of these data, suggest what features of amino acid sequence dictate the specificity of proteolytic cleavage by elastase.
c. Elastase is closely related to chymotrypsin. Suggest two kinds of amino acid residues you might expect to find in or near the active site.
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The following data describe the catalysis of cleavage of peptide bonds in
small peptides by the enzyme elastase.
Substrate
Ka(mM) ka(s")
PAPAIG
4.0
26
PAPA JA
1.5
37
PAPA ĮF
0.64
18
The arrow indicates the peptide bond cleaved in each case.
(a) If a mixture of these three substrates was presented to elastase with the
concentration of each peptide equal to 0.5 mm, which would be digested
most rapidly? Which most slowly? (Assume enzyme is present in excess.)
(b) On the basis of these data, suggest what features of amino acid sequence
dictate the specificity of proteolytic cleavage by elastase.
(c) Elastase is closely related to chymotrypsin. Suggest two kinds of amino
acid residues you might expect to find in or near the active site.
The following steps were performed using enzyme cleavage of a peptide to determine its amino acid sequence.
Step 1. FDNB yield DNB-Gly
Step 2. Treatment with trypsin yield 3 fragments: Tyr-Leu-Asp-Arg; Gly-Ser-Ala-Lys; Trp-Gly-Ser-Met
Step 3. Treatment with pepsin gave the same 3 peptide fragments.
What is the sequence of the peptide?
The trypsin enzyme is able to hydrolyze a peptide substate at the carboxyl
side of an Arg or Lys residue. However, such a reaction can be also
influenced by the amino acid residue that follows Arg or Lys. Given the
Michaelis-Menton plots obtained for two substrates (substrate A: Ser-Val-
Arg-Pro; substrate B: Ser-Val-Arg-Phe), the Km of the enzyme is higher
for:
20
Substrate A
Assume
that these
curves do
not reach
the same
limit.
15
Substrate E
0.001
0.002
0.003
(Substrate) (molar)
Inconclusive
Substrate B
Both Substrate A and B
Intitial velocity
(micromoles/literisecond)
Chapter 8 Solutions
Biochemistry: Concepts and Connections
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. 21P
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