Name: allosteric control of enzyme speed
Uploaded: 2025-10-23T11:48:33.000Z
Duration: 1 min 8 s
Channel: JoVE

Allosteric regulation is the control of an enzyme's activity through sites distinct from its active site.When an effector molecule binds to such an allosteric site, it can induce a conformational change in the enzyme.This change may increase the affinity of the enzyme's active sites for its substrates, enhancing the enzyme's activity&#8212; a process known as allosteric activation.The reaction rates for many allosteric enzymes create a positive S-shaped curve when graphed against increasing substrate concentrations.When a positive effector is added, the allosteric activation shifts the graph to a nearly hyperbolic curve.On the other hand, if the binding of the effector causes a conformational change that decreases the affinity of the enzyme for its substrate, the process is referred to as allosteric inhibition.This decrease in enzyme function can result in a reduced rate of the chemical reaction compared to the activated state.

allosteric regulation

Allosteric Regulation

Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the enzymatic activity. This alternate site is called an allosteric site, and an enzyme can contain more than one of these sites. Allosteric regulation can either be positive or negative, resulting in an increase or decrease in enzyme activity. Most enzymes that display allosteric regulation are metabolic enzymes involved in the degradation or synthesis of specific cellular molecules.Allosteric InhibitionIn allosteric inhibition, the binding of an effector molecule to the allosteric site causes a conformational change that reduces the affinity of the enzyme for the substrate. Frequently, the allosteric inhibitor is a product of the enzyme or the enzyme pathway, allowing enzymatic products to limit their own production. This type of feedback inhibition prevents overproduction of products. As a classic example, isoleucine is an allosteric inhibitor of an enzyme important in its own synthesis.Allosteric ActivationIn contrast, an allosteric activator causes a conformational change that increases the affinity of the enzyme for its substrate. Allosteric activation dramatically increases the rate of reaction, as represented by the hyperbolic curve on a reaction rate versus substrate concentration graph. As an example, extracellular ligand binding to the transmembrane EGF receptor causes a conformational change that results in an increase in the&#160; intracellular kinase activity of the receptor. If an enzyme is composed of multiple subunits, binding of an allosteric activator to a single subunit can cause an increase in affinity and shape change for all of the affiliated subunits.Suggested Reading

Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the ...

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allosteric control of enzyme speed

Allosteric control changes enzyme speed when a molecule binds to a site other than the active site. That alternate binding spot is called an allosteric site. An enzyme can have more than one allosteric site. This type of control can raise or lower enzyme activity.

Many enzymes with allosteric control are metabolic enzymes. They help with the breakdown or the building of specific molecules in cells. In allosteric inhibition, the effector molecule causes a shape change that lowers the enzyme's ability to bind its substrate. Often, the inhibitor is a product of the enzyme or pathway, so the product helps stop more of itself from being made. This feedback inhibition prevents overproduction.

A classic example is isoleucine, which acts as an allosteric inhibitor of an enzyme needed for its own synthesis. Allosteric activation works in the opposite way. An activator changes the enzyme shape so it binds its substrate more strongly. This can greatly increase reaction rate, and it is shown by a hyperbolic curve on a graph of reaction rate versus substrate concentration.

A well-known example of allosteric activation is the EGF receptor. When an extracellular ligand binds to this transmembrane receptor, it changes shape and increases the receptor's intracellular kinase activity. In enzymes with multiple subunits, binding of one activator to a single subunit can also increase the affinity and shape of the other linked subunits.

Allosteric Control of Enzyme Speed

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Allosteric control changes enzyme speed when a molecule binds to a site other than the active site. That alternate binding spot is called an allosteric site. An enzyme can have more than one allosteric site. This type of control can raise or lower enzyme activity. Many enzymes with allosteric control are metabolic enzymes. They help with the breakdown or the building of specific molecules in cells. In allosteric inhibition, the effector molecule causes a shape change that lowers the enzyme's...

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key terms and concepts

Learn how allosteric activators and inhibitors change enzyme shape, affect reaction rate, and control feedback in metabolic pathways.

Allosteric Control of Enzyme Speed | JoVE K12

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Allosteric Control of Enzyme Speed

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