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

Allosterik regülasyon, bir enzimin kendi aktif bölgesi dışında, belirli bir bölgeden kontrol edilmesidir.
 Bir molekül, allosterik bölge denilen böylesi bir bölgeye iliştiğinde, bu, uyuşumsal bir değişiklik yaratabilir veya enzim şeklini değiştirebilir.
 Bu da enzimin aktif bölgesinde sübstratlar ile birleşme eğilimini artırabilir ve enzim aktivitesini artırabilir.
Buna allosterik aktivasyon denir.
 Allosterik aktivasyon, reaksiyon hızı ve sübstrat konsantrasyonu grafiğinde pozitif, S-şekilli eğri olarak gösterilir.
 Enzimin aktive edilmesi için bir süre gereklidir.
Sonra, aktif bölgelerde ani bir artış nedeniyle yüksek bir sübstrat konsantrasyonu bağlanıp reaksiyonu yüksek oranda hızlandırabilir.
 Diğer taraftan, efektör enzime bağlanır ve üç boyutlu yapı değişikliğine neden olursa, bu, sübstratın bağlanma eğilimini azaltır.
 Bu sürece allosterik inhibisyon denir.
Bu durumda enzim fonksiyonunda düşüş yaşanır ve aktif durumdan oluşan kimyasal reaksiyon yavaşlar.

<ol><li>Cornish-Bowden, A. Enzimlerde allosterik ve işbirlikçi etkileşimleri anlamak. FEBS Dergisi. 281 (2), 621-6332 (2014).</li><li>Tsai, C.-J., Nussinov, R. Fizyolojik ve patolojik bağlamlarda EGFR aktivasyonunun ortaya çıkan allosterik mekanizması. Biyofizik Dergisi. 117 (1), 5-13 (2019).</li></ol>

allosterik düzenleme

Allosteric Regulation

Enzimlerin allosterik düzenlenmesi, bir molekülün aktif bölgeden farklı bir konuma bağlanması enzimatik aktivitede bir değişikliğe neden olduğunda meydana gelir. Bu tür bir düzenleme, enzimin aktivitesini artırarak veya azaltarak pozitif veya negatif olabilir. Alaşım sergileyen enzimlerin çoğu, belirli hücresel moleküllerin bozunmasında veya sentezinde rol oynayan metabolik enzimlerdir.

Allosterik inhibisyonda, bir molekülün allosterik bölgeye bağlanması, enzimin substrata afinitesini azaltan bir şekil değişikliğine neden olur. Sıklıkla allosterik inhibitör, enzim veya enzim yolunun bir ürünüdür ve enzimatik ürünlerin kendi üretimlerini sınırlamasına izin verir. Bu, ürünlerin aşırı üretimini önleyen bir tür geribildirim engellemesidir. Klasik bir örnek olarak izolösin, sentezinde önemli bir enzimin allosterik bir inhibitörüdür.

Bunun tersine, allosterik bir aktivatör, substrat için bir enzimin afinitesini artıran konformasyonel bir değişikliğe neden olur. Allosterik aktivasyon, S-şekilli hız-substrat reaksiyonu ile temsil edildiği gibi, reaksiyon hızını önemli ölçüde artırır. Örnek olarak, transmembran EGF reseptörüne bağlanan hücre dışı ligand, hücre içi kinaz aktivitesinin aktivasyonu ile sonuçlanan konformasyonel bir değişikliğe neden olur. Bir enzim birden fazla alt birimden oluşuyorsa, bir allosterik aktivatörün tek bir alt birime bağlanması, bağlı tüm alt birimler için afinitede bir artışa ve şekil değişikliğine neden olabilir.

Allosterik Düzenleme

Enzimlerin allosterik regülasyonu, bir efektör molekülün aktif bölgeden farklı bir bölgeye bağlanması, enzimde bir değişikliğe neden olduğunda meydana gelir.

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JoVE Core

Biology

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Cellular Processes

Hücresel Süreçler

Metabolism

Metabolizma

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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 regulation

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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