Inhibition and poisoning of enzymes

,inhibition and poisoning of enzymes ,inhibition of enzymes ,deactivation of enzymes ,poisoning of enzymes ,inhibition of carbonic anhydrase ,deactivation of carbonic anhydrase ,poisoning of carbonic anhydrase ,epoenzyme ,soft acids ,soft bases

1. INHIBITION AND POISONING OF ENZYMES CECH-612 UNIT-4(A) by - Ms Mayuri Sompura

2. Ligands can occupy an active site in an enzyme and can also coordinate strongly to the metal ion of the prosthetic group of that enzyme would naturally resist their detachment from the enzyme. Attachment of substrate with metal ion of that enzyme might inhibit the action of that enzyme. Example: if azide ion is added to enzyme carbonic anhydrase, it could occupy in active site close to Zn+2 ion of the enzyme. The azide ion would coordinate with the Zn+2 ion replacing Zn←OH2 bond with a stronger Zn ←azide bond. Consequently, the enzyme carbonic anhydrase would not get converted into hydroxy form which is active form of catalyst for the reversible hydration of carbon dioxide. by - Ms Mayuri Sompura

3. The addition of azide ion would inhibit the catalytic action of carbonic anhydrase. Addition of small amounts of CN- and H2S would inhibit the enzymatic activity of carbonic anhydrase. Sometimes heavier metal ions such as Cd+2, Hg-2, As+3 replace the metal ion of prosthetic group of an enzyme. This deactivates the enzyme. Apart from this, the heavier metal ions (soft acids) form extremely stable complexes with the S-containing amino acid units (soft bases) of the epoenzyme . by - Ms Mayuri Sompura

4. This soft acid – base interaction brings about very significant changes in the confirmation of the enzy me loses its activity as a catalyst. This is known as poisoning of catalyst. The poisoning effect of heavy metal ions can sometimes be reversed by adding S- containing ligands such as cysteine, glutathione and 2,3 dimercaptopropanol to the biological system containing the poisoned enzyme. These compound bind more strongly with the heavy metal ions than the thio groups present in epoenzymes . by - Ms Mayuri Sompura

5. Nature has devised its own mechanism of keeping away the heavy metal ion poisoning. As soon as the metallo enzyme is under attack of heavy metal ions, the concentration of thionenins ( a group of protein with high molar mass) increases in liver, kidneys and spleen. The exact mechanism for direction of presence of the presence of the heavy metal ion by the body and the reason for the production of thionenins are not yet known. by - Ms Mayuri Sompura

6. These thioneins are built from 60 condensed amino acids, one third of which are S-containing amino acid units having several free SH group. These free SH groups have strong tendency to bind with heavy metal ions (soft acid-base interactions). The thioneins therefore bind with the heavy metals ions more strongly as compared to the enzymes and thus protect the metallo enzymes from being poisoned by heavy ions. by - Ms Mayuri Sompura

7. Assignment :- Write a note on : inhibition and poisoning of enzymes by - Ms Mayuri Sompura

8. Role of alkali and alkaline earth metal ions in biological systems CECH-612 UNIT-4(A) by - Ms Mayuri Sompura