This document appears to be notes from lectures given by Dr. Ashok Kumar Jeppu on the topics of enzyme inhibition and allosteric regulation. It discusses various types of enzyme inhibition including competitive, non-competitive and irreversible inhibition. It provides examples of drugs that work through different inhibition mechanisms like DFMO and aspirin. The document also covers the concept of allosteric effectors and how binding of an allosteric effector can induce a conformational change in the enzyme to increase or decrease its activity. It gives aspartate transcarbamoylase as an example of an enzyme subjected to feedback allosteric inhibition.

1. DR.ASHOK KUMAR JEPPU
BIOCHEMISTRY
MANAGEMENT AND SCIENCE UNIVERSITY
MALAYSIA
8/27/2010
Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

4. Vmax
Km Km’ [S], mM
v
I
Vmax unchanged and Km increased
8/27/2010 4
Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

5. 1/[S]-1/Km
1/vo
1/ Vmax
Intersect at Y axis
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

10. Non-competitive Inhibition
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

11. [I] binds to free [E] or [ES] complex;
Increasing [S] can not overcome [I]
inhibition
E + S → ES → E + P
+ +
I I
↓ ↓
EI + S →EI S
←
↑ ↑
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

18. Km
[S], mM
Vmax
I
Km’
Vmax’
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

21. Difluro Methyl
Ornithine
(DFMO)-
DFMO inhibits ODC in trypanosoma
Multiplication of trypanosoma is inhibited
Effective for the treatment of trypanosomiasis
(Sleeping Sickness)
DFMO forms covalent
complex with co-enzyme
(PLP) and amino acid
residues of the enzyme
8/27/2010 21
Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

22. Allopurinol
Alloxanthine
Aspirin
acetylates a serine residue in the
active center of cyclo-oxygenase
Prostaglandin synthesis is
inhibited8/27/2010 22
Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

23. 5 - flurouracil
8/27/2010
Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
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24. Allostearic “occupying another space”
Allosteric site was first proposed by
Jacques Monod
Substances which bind to allostearic site can
modify their activity – Allosteric effector
Allosteric effectors
Substances that bind to allosteric site and
modifies the activity of the protein
8/27/2010 24
Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

25. Binding of an allosteric effector induces
conformational change in the enzyme
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
Affects the activity of the enzyme
Activity of the
enzyme increases
Activity of the
enzyme decreases
Allosteric activator Allosteric inhibitor

26. An intermediate or a product of a metabolic
pathway allosterically inhibits anenzyme
catalyzing earlier step
Feed back Allosteric Inhibition
E1 E2 E3 E4 E5 E6
A  B  C  D  E  F  G
Aspartate Transcarbamoylase
Initial step of pathway which synthesize CTP
CTP acts as allosteric inhibitor
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia

27. Thank You
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Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia