True about allosteric inhibition is-
Correct Answer: Citrate and ATP inhibiting PFK-1 is a classical example
Description: Ans. is 'b' i.e., Citrate and ATP inhibiting PFK-1 is a classical example* Allsoteric inhibition is mediated, when a regulator binds to a site, other than the catalytic site. This site is called as allosteric site, (alio means other than). Hence the allosteric regulator never binds to the active site of an enzyme.* This binding of regulator to allosteric site brings about a change in the conformation of the enzyme.* Asa result of change in conformation of the enzyme, affinity of the enzyme for the substrate in the active site is reduced.* It is a form of heterotropic allosteric regulation. Hence allosteric inhibition is not a form of homotropic allosteric regulation.* In homotropic allosteric regulation, the substrate acts as an allosteric regulator as well. Substrates always bring about allosteric stimulation, not inhibition.* Allsoteric inhibition is most commonly an exemplification of feed back inhibition or product inhibition.* Examples for allosteric inhibition are-# Citrate and ATP inhibiting Phosphofructokinase-1 (PFK-1)* PFK-1 is the rate limiting enzyme of glycolysis* ATP and citrate are products of glycolysis* Hence the products Citrate and ATP in a feed back mechanism mediate allosteric inhibition of PFK-1
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Biochemistry
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