The content includes the general introduction of enzymes their basic classification. Enzyme kinetics is described with a short view of Michaelis menten constants. Factors affecting the kinetics of enzymes are also discussed. Principles of enzyme inhibition are discussed with a few examples. The contents is prepared by the help of books, internet sources, as well as other presentations. I am thankful to all of you.

1. EnzymE kinEtics
&
PrinciPlEs of EnzymE inhibitors
Presented by: Sachin Kumar Vishwakarma
M.Pharm (Pharmaceutical Chemistry )
Presented to: Ms. Geeta Mishra
Sr. Assistant Professor, BBDNIIT, Faculty of
Pharmacy
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2. introDUction
Enzymes: Enzymes are nature’s biological catalysts
possessing the ability to promote specific chemical
reactions under the mild conditions that prevail in most
living organisms.
They are all proteins but range widely in their size from as
few as 60–70 amino acid residues as in RNase to as many
as several thousand.
The catalytic properties of an enzyme are often
dependent upon the presence of nonpeptide molecules
called cofactors or coenzymes, also known as Prosthetic
group.
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3. Enzymes are characterised by their specificity (bond
specificity, Stereospecificity, group specificity) for a
particular type of chemical reaction.
The turnover number is the maximum number of moles
of substrate that can be converted to product per
mole of enzyme in unit time. It has units of reciprocal
time in seconds. Its values range from 1 to 107 Second
inverse.
Some enzymes exist in multiple forms called isoenzymes
or isoforms that differ in amino acid sequence.
Some enzymes that promote consecutive reactions in a
metabolic pathway associate to form a multienzyme
complex.
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4. clAssificAtion of EnzymEs
By international convention, each enzyme is classified
into one of six groups on the basis of the type of
chemical reaction that it catalyses.
1.Oxidoreductases- reductases, oxidases
2.Transferases- kinases, aminotransferases
3.Hydrolases- peptidases, esterases
4.Lyases- enolase, aldolase
5.Isomerases- phosphoglucomutase glucose-6-
phosphate isomerase
6.Ligases (synthases)- carbamoyl phosphate synthase,
DNA ligase
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5. EnzymE kinEtics
Enzyme kinetics is the study of the chemical reactions
that are catalysed by enzymes.
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6. Mathematical expression of enzyme action, developed
by Leonor Michaelis and Maud Menten in 1913, two
constants, Vmax and Km, play an important role.
The maximal velocity, or Vmax, is the rate of the reaction
under these conditions.
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7. Michaelis Constant (Km) describes the substrate
concentration at which half the enzyme's active sites
are occupied by substrate.
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8. EFFECT OF TEMPERATURE: The initial rate of an
enzyme reaction varies with temperature according
to the Arrhenius equation:
rate =Ae-(E/RT)
• A is a constant known as the pre-exponential factor,
• E is the activation energy (J mol1),
• R is the gas constant (8.2 J mol1 K1), and
• T is the absolute temperature (K).
EFFECT OF pH: Due to isoelectric point enzyme get
charged so the pH should be optimum .
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9. PrinciPlEs of EnzymE inhibitors
Enzymes represent the best known biochemical catalyst,
because they are uniquely designed to carry out specific
biochemical reactions in a highly efficient manner.
Enzymes bound to substrate and form a complex.
catalysis
Enzyme product -complex
Dissociation of product and liberation of enzyme .
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10. PrinciPlEs
1. Reversible enzyme inhibition: two types
I. Competitive inhibition
II. Non-competitive inhibition
2. Irreversible enzyme inhibition
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11. rEvErsiblE EnzymE inhibition
I. Competitive inhibition: requires that the inhibitor
competes with the substrate for binding to the
enzyme at active sites, and this binding is manually
exclusive.
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12. II. Non-competitive inhibition:12

13. Examples of reversible enzyme inhibition
Inhibition of HIV – reverse transcriptase –Azidothymidine
Cancer therapy –DHFR inhibitors- Methotrexate
Angiotensin Converting Enzyme inhibition – Enalapril
Acetylcholinesterase inhibition- Physostigmin
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14. irrEvErsiblE EnzymE inhibition14

15. Examples of irreversible enzyme inhibition
Inhibition of Beta- lactamase by Clavulanic acid .
GABA-transaminase inhibition by Gabaculine.
5Alfa reductase inhibition by Finasteride
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