Definition

Enzymes or receptors with multiple binding sites exhibit a biological phenomenon called cooperativity. When an enzyme has several active sites, the binding of a substrate molecule to one site may affect the binding of a substrate molecule to another site. The binding of the second substrate may impact the binding of the third, and so forth.

This can be seen in enzymes or receptors with several binding sites where, upon the binding of a ligand to a binding site, the affinity of the binding sites for a ligand is either increased (positive cooperativity) or decreased (negative cooperativity).

Cooperativity of Enzymes

When an enzyme attaches to its substrate, its conformation changes, making it a cooperative enzyme. The enzyme can bind more substrates owing to this conformational change, speeding up the process.

Enzyme Cooperativity Binding

A cooperative binding theory describes how proteins interact with DNA and other proteins to generate functional units. According to the theory, proteins cooperate with one another to bind to DNA and other proteins through cooperative interactions. Because of their interaction, the proteins can form a complex that can execute the gene’s function.

The other enzymatic subunits are stimulated and activated when a substrate binds to one of the active sites of an enzyme. Ligands can exhibit non-cooperativity, positive cooperativity or negative cooperativity.

Positive Cooperativity

The binding of oxygen to haemoglobin is an example of positive cooperativity. The ferrous iron of a heme molecule in each of the four chains of a haemoglobin molecule can connect to one oxygen molecule. Deoxyhemoglobin has a low affinity for oxygen, but when one molecule connects to a single heme, the oxygen affinity improves, making it easier for the second molecule to bind and the third and fourth molecules to bind much more easily.

Negative Cooperativity

A phenomenon known as negative cooperativity occurs when the available receptor sites are reduced as a result of a ligand binding to a receptor site. Ligand competition is a process that occurs when there are fewer receptor sites, which reduces the ligand’s capability to bind to the receptor.

Homotropic Cooperativity

Proteins that are binding to the same ligand exhibit homotropic cooperativity, a form of mutual cooperativity. In homotropic cooperativity, the affinities with which the proteins bind the ligand increase with ligand concentration. Allosteric interactions amongst the proteins that bind to the ligand are assumed to cause this kind of homotropic cooperativity.

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Frequently Asked Questions – FAQs

Define subunit cooperativity.

Enzymes with several subunits have a tendency to cooperate to bind their substrate, which is known as subunit cooperativity. As a result, the enzyme’s affinity for its substrate increases, and its catalytic activity frequently improves.

Why is enzyme cooperativity essential?

The processes in the human body would take years to complete if there were no enzymes. Enzymes assist in reducing activation energy and speeding up the procedure. Large chain molecules composed of numerous similar subunits exhibit the cooperativity enzyme pattern as well.

What do you mean by the cooperativity of haemoglobin?

The binding of oxygen to haemoglobin is an illustration of positive cooperativity. In each of the four chains of a haemoglobin molecule, one oxygen molecule can attach to the ferrous iron of the heme molecule.

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