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DR.ASHOK KUMAR JEPPU
BIOCHEMISTRY
MANAGEMENT AND SCIENCE UNIVERSITY
MALAYSIA
8/27/2010Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia1
Vmax
Km Km’ [S], mM
v
I
Vmax unchanged and Km increased
8/27/2010 4Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
1/[S]-1/Km
1/vo
1/ Vmax
Intersect at Y axis
8/27/2010 5Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
Non-competitive Inhibition
8/27/2010 10Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
[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
←
↑ ↑
8/27/2010 11Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
Km
[S], mM
Vmax
I
Km’
Vmax’
8/27/2010 18Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
Difluro Methyl Ornithine(DFMO)-
DFMO inhibits ODC in trypanosomaMultiplication 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 21Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
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
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 effectorsSubstances that bind to allosteric site and
modifies the activity of the protein
8/27/2010 24Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia
Binding of an allosteric effector induces conformational change in the enzyme
8/27/2010 25Dr. 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
An intermediate or a product of a metabolic pathway allosterically inhibits anenzyme
catalyzing earlier stepFeed back Allosteric Inhibition
E1 E2 E3 E4 E5 E6A B C D E F G
Aspartate TranscarbamoylaseInitial step of pathway which synthesize CTP
CTP acts as allosteric inhibitor
8/27/2010 26Dr. Ashok KUmar J; ; Department of Biochemistry. MSU,
Malaysia