Question
Describe any four classes of enzymes. Make distinction between prosthetic group and coenzymes.
✓
Answer
Classes of enzymes
- Class 1: Oxidoreductases:
- These enzymes catalyse the oxidation (by adding oxygen or removal of hydrogen or removal of electrons) or reduction (by adding hydrogen or adding electrons to a substrate) of a substance.
- Class 2: Transferases:
- These enzymes catalyse the transfer of specific groups from one substrate to another.
- Class 3: Hydrolases:
- These enzymes catalyse the breakdown of larger molecules into smaller molecules with the addition of water.
- Class 4: Lyases:
- These enzymes catalyse the cleavage of specific covalent bonds and removal of specific group(s), without the use of water.
- Class 5: Isomerases:
- These enzymes catalyse the rearrangement of atoms in a molecule to form isomers.
- Class 6: Ligases:
- These enzymes catalyse covalent bonding (of C - O, C - S, C - N, P - O etc.) between two substrates to form a large molecule, mostly involving utilisation of energy by hydrolysis of ATP.
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S. No.
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Prosthetic Group
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Coenzyme
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1.
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It is a non-protein organic moiety, that is tightly bound to the apoenzyme.
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It is a non-protein organic moiety, that is loosely bound to the apoenzyme.
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2.
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It is a permanent association, e.g., Haem in peroxidases.
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Its association is more often transient, e.g., NAD in dehydrogenases.
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