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

- La régulation allostérique fait référence au contrôled'une enzyme par un site distinct,autre que le site actif des enzymes. 
Quand une molécule se lie à un tel endroit,appelé site allostérique. 
La fixation peut induire un changement de conformation,ou un changement de forme de l'enzyme. 
Cette action peut augmenter l'affinitédes sites actifs des enzymes pour ses substrats,augmentant ainsi l'activité des enzymes. 
Un processus appelé activation allostérique. 
Dans un graphique de la réaction,la concentration du substrat,l'activation allostérique peut être représentéesous la forme d'une courbe positive en S. 
Là où il y a un temps de latenceavant que l'enzyme soit activée. 
Aavec l'augmentation soudaine des sites actifs,une forte concentration de substrat peut se lieret accélérer rapidement la réaction. 
D'autre part, si l'effecteur se lie à l'enzymeet provoque un changement de conformationqui diminue l'affinité de la liaison au substrat,le processus est appelé inhibition allostérique. 
Il y a alors une diminution de la fonction enzymatiqueet une diminutionde la vitesse de la réaction chimiquede l'état activé.

<ol><li>Cornish‐Bowden, A. Comprendre les interactions allostériques et coopératives dans les enzymes. Le journal de la FEBS. 281 (2), 621-6332 (2014).</li><li>Tsai, C.-J., Nussinov, R. Mécanisme allostérique émergent de l’activation de l’EGFR dans des contextes physiologiques et pathologiques. Journal biophysique. 117 (1), 5 à 13 (2019).</li></ol>

régulation allostérique

Allosteric Regulation

La régulation allostérique des enzymes se produit lorsque la liaison d’une molécule à un endroit différent du site actif provoque un changement dans l’activité enzymatique. Ce type de régulation peut être positif ou négatif, augmentant ou diminuant l’activité de l’enzyme. La plupart des enzymes qui présentent une allostérie sont des enzymes métaboliques impliquées dans la dégradation ou la synthèse de molécules cellulaires spécifiques.
 
 Dans l’inhibition allostérique, la liaison d’une molécule au site allostérique provoque un changement de forme qui réduit l’affinité de l’enzyme pour le substrat. Fréquemment, l’inhibiteur allostérique est un produit de l’enzyme ou de la voie enzymatique, permettant aux produits enzymatiques de limiter leur propre production. Il s’agit d’un type de rétro-inhibition, empêchant une surproduction de produits. À titre d’exemple classique, l’isoleucine est un inhibiteur allostérique d’une enzyme importante dans sa synthèse.
 
 En revanche, un activateur allostérique provoque un changement conformationnel qui augmente l’affinité d’une enzyme pour le substrat. L’activation allostérique augmente considérablement la vitesse de réaction, telle que représentée par la réaction d’un substrat avec une vitesse en forme de S. À titre d’exemple, la liaison extracellulaire de ligand au récepteur transmembranaire EGF provoque un changement conformationnel qui entraîne l’activation de l’activité intracellulaire de kinase. Si une enzyme est composée de plusieurs sous-unités, la liaison d’un activateur allostérique à une seule sous-unité peut provoquer une augmentation de l’affinité, et un changement de forme, pour toutes les sous-unités affiliées.

Régulation allostérique

La régulation allostérique des enzymes se produit lorsque la liaison d’une molécule effectrice à un site différent du site actif provoque une modification de la ...

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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.

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Allosteric Control of Enzyme Speed

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