Enzyme Catalysis

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Enzyme Catalysis Chapter 11
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Table 11-1
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Table 11-2
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Figure 11-1
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Figure 11-2
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Figure 11-3
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Figure 11-4
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Figure 11-5b
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Figure 11-7
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Box 11-1
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Figure 11-9
RNase S complexed with a nonhydrolyzable
substrate.
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Figure 11-10 Catalytic mechanism of RNase A.
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Figure 11-10 part 1
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Figure 11-10 part 2
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Figure 11-12 Biologically Important Nucleophiles
and Electrophiles
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Figure 11-13a Carbonic Anhydrase. See
interactive exercise 7.
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Figure 11-13b
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Figure 11-15
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Box 11-3a
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Box 11-3b
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Box 11-3c
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Serine Proteases
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Table 15-4 A Selection of Serine Proteases.
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Figure 11-24
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Figure 11-25 Trypsin
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Figure 11-26
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Figure 11-27
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Figure 11-28
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Figure 11-29
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Figure 11-29 Catalytic mechanism ofthe serine
proteases.
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Catalytic mechanism of the serine proteases.
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Catalytic mechanism of the serine proteases.
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Catalytic mechanism of the serine proteases.
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Catalytic mechanism of the serine proteases.
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Figure 11-30a
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Figure 11-30b
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Figure 15-22 Relative positions of the active
site residues in subtilisin, chymotrypsin, serine
carboxypeptidase II, and ClpP protease.
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Example of convergent evolution.
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Figure 11-31 Trypsin and Bovine Pancreatic
Trypsin Inhibitor
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Figure 11-33
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Box 11-4a
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Box 11-4b
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Box 11-4c
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Enzyme Kinetics, Chapter 12
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Figure 14-7 Progress curves for the components
of a simple MichaelisMenten reaction.
After the first few milliseconds of a reaction,
a steady state is attained.
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k2
k1
E S ?ES?EP
k-1
(k-2 is negligible until products start to build
up)
Steady state conditions--ES remains relatively
constant over the course of the rxn until S
starts runing out.
Vo k2ES
k1ES k-1ES k2ES (k-1 k2)ES
Define a new constant ES/ES (k-1 k2)/
k1 KM
KmES SE
KmES ETS-ESS
E ET -ES
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ES(KM S) ETS
(ETS
And ES v/k2
ES ------------------- KM S
k2ETS
Define Vmaxk2ET
v ------------------ KM S
vmaxS
Michaelis-Menton equation
v ----------------- KM S
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Figure 14-8 Plot of the initial velocity vo of a
simple MichaelisMenten reaction versus the
substrate concentration S.
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An enzyme obeys Michaelis-Menten kinetics
with Vmax 1.8 umol ml-1 s-1 at an enzyme
concentration of 15 umol ml-1. Calculate kcat
and KM for the enzyme. Is the value you obtain
for KM what you would expect given your data?
Why or why not? S uM vo (umol ml-1
s-1) 1600 1.39 800 1.13 400 0.83 200
0.54 100 0.32
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An enzyme obeys Michaelis-Menten kinetics
with Vmax 1.8 umol ml-1 s-1 at an enzyme
concentration of 15 umol ml-1. Calculate kcat
and KM for the enzyme. Is the value you obtain
for KM what you would expect given your data?
Why or why not? S mM vo (mmol ml-1
s-1) 1600 1.39 800 1.13 400 0.83 200 0.
54 100 0.32
Ans kcat 0.12 s-1 KM 470 mM
Yes.
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New Kinetic Parameter
Kcat Vmax ET
when Kcat ltltS
Turnover Number
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Previously defined Vo k2ES and ES
ES KM
Vo kcatES/KM
When SltltKM. E?ET
Vo kcatETS/KM
Kcat/KM rate constant for interaction of E and
S (turnover number) Can be used to measure an
enzymes preference for different substrates.
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Table 12-1
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Figure 12-4
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Figure 12-5
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Figure 12-6
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Figure 12-7
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Table 12-2
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Figure 12-8
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Figure 12-9
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Box 12-4a
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Box 12-4b
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Box 12-4c
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Figure 12-10
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Figure 12-11
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Figure 12-12
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Figure 12-13
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e.g. Glycogen Phosphorylase
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Figure 12-14a
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Figure 12-14b
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Figure 12-15
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Figure 12-16