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

Regulacja allosteryczna to kontrola aktywności enzymu poprzez miejsca odrębne od jego miejsca aktywnego.Kiedy cząsteczka efektorowa wiąże się z takim miejscem allosterycznym, może wywołać zmianę konformacyjną enzymu.Ta zmiana może zwiększyć powinowactwo miejsc aktywnych enzymu do jego substratów, zwiększając aktywność enzymu - proces znany jako aktywacja allosteryczna.Szybkości reakcji dla wielu enzymów allosterycznych tworzą dodatnią krzywą w kształcie litery S, gdy są przedstawiane na wykresie w stosunku do rosnących stężeń substratów.Po dodaniu dodatniego efektora aktywacja allosteryczna przesuwa wykres do prawie hiperbolicznej krzywej.Z drugiej strony, jeśli wiązanie efektora powoduje zmianę konformacyjną, która zmniejsza powinowactwo enzymu do jego substratu, proces ten określa się mianem hamowania allosterycznego.To zmniejszenie funkcji enzymu może skutkować zmniejszoną szybkością reakcji chemicznej w porównaniu ze stanem aktywowanym.

<ol><li>Cornish-Bowden, A. Zrozumienie oddziaływań allosterycznych i kooperacyjnych w enzymach. Czasopismo FEBS. 281 (2), 621-6332 (2014).</li><li>Tsai, C.-J., Nussinov, R. Pojawiający się allosteryczny mechanizm aktywacji EGFR w kontekstach fizjologicznych i patologicznych. Czasopismo biofizyczne. 117 (1), 5-13 (2019).</li></ol>

regulacja allosteryczna

Allosteric Regulation

Allosteryczna regulacja enzymów zachodzi, gdy wiązanie cząsteczki efektorowej z miejscem innym niż miejsce aktywne powoduje zmianę aktywności enzymatycznej. To alternatywne miejsce nazywa się miejscem allosterycznym i enzym może zawierać więcej niż jedno z tych miejsc. Regulacja allosteryczna może być dodatnia lub ujemna, co powoduje wzrost lub spadek aktywności enzymu. Większość enzymów wykazujących regulację allosteryczną to enzymy metaboliczne zaangażowane w degradację lub syntezę określonych cząsteczek komórkowych.

Inhibicja allosteryczna

W inhibicji allosterycznej wiązanie cząsteczki efektorowej do miejsca allosterycznego powoduje zmianę konformacyjną, która zmniejsza powinowactwo enzymu do substratu. Często inhibitor allosteryczny jest produktem enzymu lub szlaku enzymatycznego, umożliwiając produktom enzymatycznym ograniczenie własnej produkcji. Ten rodzaj inhibicji przez sprzężenie zwrotne zapobiega nadprodukcji produktów. Klasycznym przykładem jest izoleucyna, która jest allosterycznym inhibitorem enzymu ważnego w jego własnej syntezie.

Aktywacja allosteryczna

Z kolei aktywator allosteryczny powoduje zmianę konformacyjną zwiększającą powinowactwo enzymu do substratu. Aktywacja allosteryczna radykalnie zwiększa szybkość reakcji, co przedstawia hiperboliczna krzywa na wykresie szybkości reakcji w funkcji stężenia substratu. Na przykład zewnątrzkomórkowe wiązanie ligandu z transbłonowym receptorem EGF powoduje zmianę konformacyjną, która skutkuje wzrostem wewnątrzkomórkowej aktywności kinazy receptora. Jeśli enzym składa się z wielu podjednostek, wiązanie aktywatora allosterycznego z pojedynczą podjednostką może spowodować wzrost powinowactwa i zmianę kształtu wszystkich powiązanych podjednostek.

Sugerowana lektura

Regulacja allosteryczna

Allosteryczna regulacja enzymów zachodzi, gdy wiązanie cząsteczki efektora z miejscem innym niż miejsce aktywne powoduje zmianę w ...

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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

what is metabolism?

Metabolism, Energy, and Cell Reactions

Metabolism is the set of chemical reactions that happen in a cell. It includes anabolism, which builds molecules, and catabolism, which breaks them down. These reactions help cells manage energy and keep life processes running. Cells use metabolism to turn food into energy, make cell parts, and remove waste products. Food stores potential energy in the bonds between atoms. Catabolic pathways break large food molecules into smaller ones and release that energy. Anabolic pathways use that energy...

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Entropy in Food Web Energy Flow

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enzyme kinetics

Substrate Effects on Enzyme Rates

Enzyme kinetics examines how enzymes change the rate of a reaction. Enzymes speed reactions by lowering the activation energy of the reactants. The reaction rate is the speed at which an enzyme turns reactants into products, and it can be affected by several factors, including the number of available reactants. Scientists often study enzyme kinetics in a test tube with a fixed amount of enzyme. When more substrate, or reactant, is added, the reaction rate increases because the enzyme can make...

enzyme inhibition

Competitive vs Noncompetitive Inhibitors

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feedback inhibition

How Cells Control Product Buildup

Cells use enzymes to run biochemical reactions and make the products they need. These reactions are happening constantly, and enzymes speed them up so they happen fast enough to matter. Enzyme activity also has to be regulated. Cells need the right amounts of starting materials, intermediate metabolites, and final products. If these substances build up too much or drop too low, the cell can be harmed. That is why cells use control systems to keep metabolic levels balanced. One important...

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...

cofactors and coenzymes

Enzyme Helpers: Metals, Vitamins, and More

Enzyme helpers are needed for many enzymes to work properly. These helpers fall into two groups: cofactors and coenzymes. Cofactors are metallic ions, while coenzymes are non-protein organic molecules. Both can be tightly bound to an enzyme or attach only when the substrate binds. Cofactors are common in mature proteins, appearing in about 30% of them. They are often added as the enzyme folds and help with catalytic activity. Magnesium is one important cofactor, and it is needed by more than...

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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