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

- [Verteller] Allosterische regulering verwijst naar de regulatie van een enzym via een andere plaats dan de actieve plaats van het enzym. Wanneer een molecuul zich bindt aan een dergelijke locatie, de allosterische plaats genoemd, kan de binding een conformationele verandering, of vormverandering, in het enzym veroorzaken. Een dergelijke actie kan leiden tot een verhoging van de affiniteit van de actieve plaatsen van het enzym voor zijn substraten, waardoor de activiteit van het enzym wordt versterkt, een proces dat bekend staat als allosterische activering.

In een reactiesnelheid/substraatconcentratie grafiek kan allosterische activering worden weergegeven als een positieve S-vormige curve, waarbij er een vertragingstijd is tot het enzym wordt geactiveerd. Door de plotselinge toename van het aantal actieve plaatsen kan een hoge concentratie van het substraat zich dan binden en de reactie snel versnellen. Aan de andere kant, als de effector zich aan het enzym bindt en een conformationele verandering veroorzaakt die de affiniteit van substraatbinding vermindert, wordt het proces allosterische onderdrukking genoemd.

In dit geval is er een afname van de werking van het enzym en een afname van de chemische reactie uit de geactiveerde toestand.

allosterische regulatie

Allosteric Regulation

Allosterische regulatie van enzymen vindt plaats wanneer de binding van een effectormolecuul aan een plaats die verschilt van de actieve plaats een verandering in de enzymatische activiteit veroorzaakt. Deze alternatieve plaats wordt een allosterische plaats genoemd en een enzym kan meer dan één van deze plaatsen bevatten. Allosterische regulatie kan positief of negatief zijn, wat resulteert in een toename of afname van de enzymactiviteit. De meeste enzymen die allosterische regulatie vertonen, zijn metabolische enzymen die betrokken zijn bij de afbraak of synthese van specifieke cellulaire moleculen.

Allosterische remming

Bij allosterische remming veroorzaakt de binding van een effectormolecuul aan de allosterische plaats een conformationele verandering die de affiniteit van het enzym voor het substraat vermindert. Vaak is de allosterische remmer een product van het enzym of de enzymroute, waardoor enzymatische producten hun eigen productie kunnen beperken. Dit type feedbackremming voorkomt overproductie van producten. Als klassiek voorbeeld is isoleucine een allosterische remmer van een enzym dat belangrijk is bij zijn eigen synthese.

Allosterische activering

Daarentegen veroorzaakt een allosterische activator een conformationele verandering die de affiniteit van het enzym voor zijn substraat verhoogt. Allosterische activering verhoogt de reactiesnelheid dramatisch, zoals weergegeven door de hyperbolische curve in een grafiek van reactiesnelheid versus substraatconcentratie. Extracellulaire ligandbinding aan de transmembraan EGF-receptor veroorzaakt bijvoorbeeld een conformationele verandering die resulteert in een toename van de lichaamstemperatuur. intracellulaire kinase-activiteit van de receptor. Als een enzym uit meerdere subeenheden bestaat, kan de binding van een allosterische activator aan een enkele subeenheid een toename van de affiniteit en vormverandering voor alle aangesloten subeenheden veroorzaken.

Allosterische regulatie

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.

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Allosteric Control of Enzyme Speed

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