Presentation of Enzyme inhibitaion

Enzyme inhibition and its types.

1. ENZYME INHIBITION PRESENTED BY KEHKASHAN SABIR M.PHIl CHEMISTRY SARHAD UNIVERSITY PESHAWAR

2. Introduction Types of Inhibitors Irreversible inhibitor Reversible inhibitor Competitive inhibitor Non competitive inhibitor Un competitive inhibitor CONTENTS

3. INHIBITORS A chemical substance which can react in place of substrate with the enzyme but is not transferred into products and block the active site of the enzyme temporarily or permanently is called inhibitors. For example, poisons like cyanide and antibodies.

4. TYPES OF ENZYME INHIBITION Irreversible inhibitors Reversible inhibitors

5. IRREVERSIBLE ENZYME Irreversible inhibitors occupy or destroy the active site of an enzyme permanently. They form strong covalent bond with the active site. Sometimes they physically block the active site.

6. EXAMPLES Very small concentrate of chemical reagents such as heavy metals ions , M ercury (Hg), Silver (Ag) and Arsenic (As) or certain iodine containing compounds completely inhibit some enzymes.

7. REVERSIBLE INHIBITORS They form weak linkage with the enzyme. There effect is completely or partially neutralized by increasing the concentration of substrate. They are further divided into 3 types: Competitive Inhibitor Non Competitive Inhibitor Uncompetitive Inhibitor

8. COMPETITIVE INHIBITORS A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate. The inhibitor competes for the same active site as the substrate molecule. A competitive inhibitor is usually reversible if sufficient substrate molecules are available to ultimately displace the inhibitor.

9. Therefore, the amount of enzyme inhibition depends upon the inhibitor concentration, substrate concentration and the relative affinity of the inhibitor and substrate for the active site

10. EXAMPLE Sulfonamides, or sulfa drugs, are structurally related to sulfanilamide, an analog of p- aminobenzoic acid, or PABA.

11. NON-COMPETITIVE INHIBITORS A Non-competitive inhibitor is a substance that interact with the enzyme, but usually not at the active site. The net effect of a non-competitive inhibitor is to change the shape of the enzyme and thus the active site, so that the substrate can no longer interact with the enzyme to give a reaction. This inhibitor is usually reversible.

12. EXAMPLE An example of a use for a non-competitive inhibitor is in the use of cyanide as a poison (prevents aerobic respiration). Cyanide is a poison which prevents ATP production via aerobic respiration, leading to eventual death.

13. UNCOMPETITVE INHIBITOR Uncompetitive inhibitors bind only to the enzyme-substrate complex and not to the free enzyme.

14. EXAMPLES Drugs to treat causes of poisoning by m ethanol or ethylene glycol act as uncompetitive inhibitors.