(DEC 2006)
54. If an enzyme obeying Hills reaction shows negative cooperativity. It means
(1) Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units
(2) Binding of substrate to any one site of single subunit enzyme decreases affinity for other substrate
(3) Binding of substrate to any one site of multi-subunit enzyme increases affinity for other substrate to other sub-units
(4) Binding of substrate to any one site of multi-subunit enzyme makes enzyme non-functional
The correct answer is (1) Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Introduction
Negative cooperativity is an important regulatory phenomenon in multimeric enzymes that affects substrate binding and enzymatic activity. When substrate binding to one subunit decreases the affinity of other subunits for the substrate, the enzyme exhibits negative cooperativity. This differs from positive cooperativity where substrate binding enhances affinity at other sites. Negative cooperativity provides a nuanced control mechanism, preventing over-activation and offering graded responses to substrate concentration changes.
Explanation of Negative Cooperativity
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Definition: Binding of substrate to one active site of a multi-subunit enzyme reduces the binding affinity of other active sites for the substrate.
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This results in less pronounced substrate saturation and a more gradual increase in enzyme activity with increasing substrate concentration.
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The substrate binding curve is less sigmoidal and more hyperbolic but with reduced steepness compared to non-cooperative enzymes.
Why Negative Cooperativity Occurs
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Induces allosteric conformational changes upon substrate binding.
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Structural alterations in one subunit reduce the likelihood of substrate binding to neighboring subunits.
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Ensures fine-tuned enzymatic regulation preventing excessive substrate turnover.
Biological Significance
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Helps maintain metabolic balance by avoiding sharp reactions to substrate fluctuations.
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Found in various enzymes involved in metabolism and signaling.
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Facilitates graded control in response to changing cellular environments.
Incorrect Options Overview
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(2) Single subunit enzymes cannot exhibit cooperativity as they have only one binding site.
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(3) Describes positive cooperativity, increasing affinity upon substrate binding, opposite of negative cooperativity.
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(4) Binding at one site does not “disable” the enzyme but modulates affinity elsewhere.
Summary Table
| Statement Number | Explanation | Correctness |
|---|---|---|
| (1) | Substrate binding decreases affinity at other subunits (negative cooperativity) | Correct |
| (2) | Single subunit enzymes do not show cooperativity | Incorrect |
| (3) | Binding increases affinity (positive cooperativity) | Incorrect |
| (4) | Binding makes enzyme non-functional (false) | Incorrect |
Conclusion
Negative cooperativity, where substrate binding to one site of a multi-subunit enzyme decreases other sites’ affinity, is a key mechanism for the delicate control of enzyme activity. This mechanism contrasts with positive cooperativity and is specific to multi-subunit proteins, making option (1) the accurate choice.
This detailed explanation aids students and researchers in recognizing and understanding enzyme cooperativity types, crucial for interpreting kinetic data and enzyme regulation in biological systems.
36 Comments
Khushi Vaishnav
September 12, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Varsha Tatla
September 13, 2025Option 1st will be absolutely right 👍🏿
Kajal
September 13, 2025In Hill reaction showing negative cooperation binding of one subunit decrease affinity for next subunit so option 1 is correct.
Kanica Sunwalka
September 13, 2025option 1 is correct
Aakansha sharma Sharma
September 13, 2025The correct answer is (1) Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Rishita
September 14, 20251st is the right answer
Pratibha Jain
September 14, 2025correct answer is option (1)
Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Mohd juber Ali
September 14, 2025Option 1 is right in negative co opretion affinity decrease and km increase
Santosh Saini
September 14, 2025Option 1st is right bcz in nagetive cooperation affinity decrease and dissociation increase
Anju
September 14, 2025Ans:1
Negative cooperation decrease the affinity for binding of other molecule
Dharmpal Swami
September 14, 2025In negative cooperation affinity are decrease and dissociation increase
yashika
September 14, 2025Hill : binding of one site inmulti subunit decrease affinity for other subunit
Pooja
September 14, 2025Option a is correct
Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units
Muskan singodiya
September 14, 2025Option 1 because negative cooperation m affinity decrease and dissociation increase
Konika Naval
September 14, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units
Soniya Shekhawat
September 14, 2025Binding of substrate to one active site of a multi-subunit enzyme reduces the binding affinity of other active sites for the substrate. So option 1 is correct .
Aafreen Khan
September 14, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units. So 1st is correct answer
Kirti Agarwal
September 14, 2025Opt a
Pallavi Ghangas
September 14, 2025In negative corporation binding of one substrate inhibits the binding of other substrate in a multi subunit enzyme
Sakshi Kanwar
September 14, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units. 1
Sakshi yadav
September 14, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub unit
Palak Sharma
September 14, 20251) Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Priya dhakad
September 14, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units
Deepika sheoran
September 15, 2025Binding of substrate to any one site of multi sub unit enzyme decrease affinity for other substrate to other sub units.
Roopal Sharma
September 15, 2025Substrate binding at one sub unit of multi sub unit enzyme decrease affinity.
Parul
September 15, 2025Negative cooperativity means binding of substrate to any one site of multimeric enzyme decreases affinity for other substrate to other sub-units.
Bhawna Choudhary
September 15, 2025In negative cooperation binding of first substrate of any one site of multi subunit enzyme decrease the affinity of other substrate
Anjana sharma
September 16, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units
Khushi Agarwal
September 16, 2025If an enzyme obeying Hills reaction shows negative cooperativity. It means
(1) Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units
Nilofar Khan
September 16, 2025correct answer is (1)
Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Tanvi Panwar
September 16, 2025Binding of substrate to any site of multi subunit enzyme decreases affinity for other substrate to other sub-units.
Simran Saini
September 17, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Avni
September 17, 2025The correct answer is (1) Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.
Priya khandal
September 17, 20251is right 👍
Minal Sethi
September 19, 2025Binding of substrate to any one site of multi subunit enzyme decreases affinity for other substrates
Muskan Yadav
September 19, 2025Binding of substrate to any one site of multi-subunit enzyme decreases affinity for other substrate to other sub-units.