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

Die allosterische Regulation bezieht sich auf die Kontrolle eines Enzyms durch eine andere Stelle als die aktive Stelle des Enzyms.
 Wenn ein Molekül sich an einen solchen Ort bindet, der als allosterische Stelle bezeichnet wird.
 Die Bindung kann eine Konformationsänderung oder eine Formänderung im Enzym induzieren.
 Eine solche Wirkung kann eine Erhöhung der Affinität der aktiven Zentren des Enzyms zu seinen Substraten verursachen, wodurch die Aktivität des Enzyms erhöht wird.
 Ein Prozess, der als allosterische Aktivierung bekannt ist.
 In einem Reaktionsgeschwindigkeits-Substratkonzentrations- Diagramm kann die allosterische Aktivierung als positive S-förmige Kurve dargestellt werden.
 Wo es eine Verzögerungszeit gibt, bis das Enzym aktiviert wird.
 Dann kann aufgrund des plötzlichen Anstiegs der aktiven Stellen eine hohe Substratkonzentration binden und die Reaktion schnell beschleunigen.
 Wenn sich andererseits der Effektor an das Enzym bindet und eine Konformationsänderung verursacht, die die Affinität der Substratbindung verringert, wird der Prozess als allosterische Hemmung bezeichnet.
 In diesem Fall gibt es eine Abnahme der Enzymfunktion und einen Abfall der Geschwindigkeit der chemischen Reaktion aus dem aktivierten Zustand.

<ol><li>Cornish-Bowden, A. Verständnis allosterischer und kooperativer Wechselwirkungen in Enzymen. Das FEBS Journal. 281 (2), 621-6332 (2014).</li><li>Tsai, C.-J., Nussinov, R. Aufkommender allosterischer Mechanismus der EGFR-Aktivierung in physiologischen und pathologischen Kontexten. Biophysikalische Zeitschrift. 117 (1), 5-13 (2019).</li></ol>

allosterische regulation

Allosteric Regulation

Die allosterische Regulation von Enzymen tritt auf, wenn die Bindung eines Moleküls an einer anderen Stelle als dem aktiven Zentrum eine Veränderung der enzymatischen Aktivität bewirkt. Diese Art der Regulierung kann entweder positiv oder negativ sein. Die Enzymaktivität wird entweder erhöht oder vermindert. Die meisten Enzyme, die eine Allosterie aufweisen, sind Stoffwechselenzyme. Sie nehmen am Abbau oder an der Synthese spezifischer Zellmoleküle teil.
 
 Bei der allosterischen Hemmung bewirkt die Molekülbindung an der allosterischen Stelle eine Strukturveränderung, wodurch die Affinität des Enzyms zum Substrat verringert wird. Häufig ist der allosterische Inhibitor ein Produkt des Enzyms oder des Signalweges des Enzyms, wodurch die enzymatischen Produkte ihre eigene Produktion einschränken können. Dies ist eine Art der Rückkopplungshemmung, bei der eine Überproduktion von Stoffen verhindert wird. Ein klassisches Beispiel ist Isoleucin, da es ein allosterischer Inhibitor eines Enzyms ist, welches wichtig für seine Synthese ist.
 
 Im Gegensatz dazu bewirkt ein allosterischer Aktivator eine Veränderung der Konformation des Substrats. Diese erhöht die Affinität des Enzyms zum Substrat. Die allosterische Aktivierung erhöht dramatisch die Reaktionsgeschwindigkeit, was durch eine S-förmige Geschwindigkeit-Substrat-Kurve dargestellt wird. Als Beispiel verursacht die Bindung des extrazellulären Liganden an den transmembranen EGF-Rezeptor eine Konformationsänderung, die zur Aktivierung der intrazellulären Kinaseaktivität führt. Wenn ein Enzym aus mehreren Untereinheiten zusammengesetzt ist, kann die Bindung eines allosterischen Aktivators an eine einzige Untereinheit eine Erhöhung der Affinität und eine Formveränderung für alle verbundenen Untereinheiten hervorrufen.

Allosterische Regulation

Die allosterische Regulation von Enzymen tritt auf, wenn die Bindung eines Effektormoleküls an eine Stelle, die sich von der aktiven Stelle unterscheidet, eine Veränderung der ...

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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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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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