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

A regulação alostérica refere-se ao controle de uma enzima através de um local distinto, diferente do local ativo da enzima. Quando uma molécula se liga a tal local, chamado de sítio alostérico, a ligação pode induzir uma mudança de conformação, ou mudança de forma, na enzima. Tal ação pode causar um aumento na afinidade do sítio da enzima ativa para seus substratos, aumentando a atividade das enzimas, um processo conhecido como ativação alostérica.Num gráfico de concentração de taxa de reação-substrato, ativação alostérica pode ser representada como uma curva em forma de S positiva, onde há um atraso até que a enzima seja ativada. Então, devido ao súbito aumento de sítios ativos, uma alta concentração de substrato pode ligar e rapidamente acelerar a reação. Por outro lado, se o efetor se ligar à enzima e causar uma mudança na conformação que diminui a afinidade de ligação ao substrato, o processo é referido como inibição alostérica.Neste caso, existe uma diminuição da função enzimática, e uma queda na taxa da reação química a partir do estado ativado. temperatura, como quando mudanças sazonais induzem modificações na composição de ácidos graxos dos peixes.

<ol><li>Cornish-Bowden, A. Compreendendo as interações alostéricas e cooperativas em enzimas. O Jornal FEBS. 281 (2), 621-6332 (2014).</li><li>Tsai, C.-J., Nussinov, R. Mecanismo alostérico emergente de ativação do EGFR em contextos fisiológicos e patológicos. Revista Biofísica. 117 (1), 5-13 (2019).</li></ol>

regulação alostérica

Allosteric Regulation

A regulação alostérica de enzimas ocorre quando a ligação de uma molécula a um local diferente do local ativo causa uma mudança na atividade enzimática. Esse tipo de regulação pode ser positiva ou negativa, aumentando ou diminuindo a atividade da enzima. A maioria das enzimas que exibem a alosteria são enzimas metabólicas envolvidas na degradação ou síntese de moléculas celulares específicas.
 
 Na inibição alostérica, a ligação de uma molécula ao local alostérico causa uma mudança de forma que reduz a afinidade da enzima para o substrato. Frequentemente, o inibidor alostérico é um produto da enzima ou da via enzimática, permitindo que produtos enzimáticos limitem a sua própria produção. Trata-se de um tipo de inibição por feedback, prevenindo a superprodução de produtos. Como exemplo clássico, a isoleucina é um inibidor alostérico de uma enzima importante para a sua síntese.
 
 Em contraste, um ativador alostérico causa uma mudança conformacional que aumenta a afinidade de uma enzima para o substrato. A ativação alostérica aumenta drasticamente a velocidade da reação, representada por uma reação de velocidade-substrato em forma de S. Como exemplo, a ligação de ligandos extracelulares ao receptor de EGF transmembranar causa uma alteração conformacional que resulta na ativação da atividade de quinases intracelulares. Se uma enzima é composta por múltiplas subunidades, a ligação de um ativador alostérico a uma única subunidade pode causar um aumento na afinidade, e alteração de forma, em todas as subunidades afiliadas.

Regulação Alostérica

A regulação alostérica de enzimas ocorre quando a ligação de uma molécula efetora a um sítio diferente do sítio ativo causa uma alteração no ...

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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 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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