Explain briefly the Function of allosteric enzyme

Hello aspirant,

First of all we have to know about Allosteric enzymes

• These are the enzymes has one catalytic site where the substrate binds and another separate Allosteric site where modifier binds
• The binding of modifier either may enhance the reaction(positive modifier) or it slows down the reaction (negative modifier)

Our body uses Allosteric enzymes as key enzymes in metabolic pathways.

For Eg: phosphofructokinase(glycolysis),ALA synthase(heme synthesis),pyruvate carboxylase(Krebs cycle),Acetyl-CoA carboxylase(Krebs cycle),carbamoyl phosphate synthetase-1(urea cycle).

1. Key enzymes

• The phosphofructoKinase enzymes is the 3rd step in glycolysis pathway and it the committed step(Allosteric enzyme) in the glycolysis
• If the cellular ATP level increases this ATP binds the Allosteric site of the enzyme and inhibits the reaction glycolysis is slowed down
• If cellular AMP is high ultimately binds to Allosteric site of the enzyme it increases the reaction hence the glycolysis is enhanced

2. Feedback inhibition

• Means the end product of any pathway inhibits the own enzyme activity
• Eg:in heme synthesis the ALA synthase enzyme inactivated by final product heme when it increases

3. Induction & repression

The activity of the enzymes may increase or decrease on its gene level itself by modification on operator site of the gene

Eg:ALA synthase activity is enhanced by barbiturates and it is autorgulated by heme itself

4. Covalent modification

• The activity of enzymes may increase or decrease by addition of a group
• Eg:Zymogen activation by partial proteolysis it is a reversible

5. Compartmentalization

• Certain group of enzymes for certain pathways are localised in certain areas of body
• For Eg: in heme synthesis,urea cycle the group of enzymes are located in mitochondria and cytoplasm and rgulates the pathway

Hope this helps you

Feel free to ask any questions

All the best for your future