Name: competitive vs noncompetitive inhibitors
Uploaded: 2025-10-23T11:48:34.000Z
Duration: 1 min 30 s
Channel: JoVE

Określone substancje chemiczne mogą regulować działanie enzymów poprzez hamowanie lub blokowanie ich funkcji. Inhibitory enzymów występują w dwóch różnych formach: konkurencyjnej i niekonkurencyjnej.
Inhibitor kompetycyjny jest na tyle podobny do specyficznego substratu enzymu, że może wiązać się z miejscem aktywnym i blokować wiązanie substratu. To działanie zasadniczo zmniejsza liczbę enzymów dostępnych do wiązania się z substratem.
W przeciwieństwie do tego, niekonkurencyjny inhibitor będzie wiązał się z miejscem aktywnym, ale nadal będzie na nie wpływał, na przykład poprzez zmianę kształtu enzymu i znaczne zmniejszenie powinowactwa do wiązania substratu z miejscem aktywnym, uniemożliwiając prawidłowe funkcjonowanie enzymu.
Ponadto oba typy inhibitorów w różny sposób wpływają na szybkość reakcji chemicznej.
W porównaniu z kontrolą, normalną szybkością reakcji enzymatycznej, reakcja obejmująca inhibitor kompetycyjny potrzebowałaby więcej czasu, aby osiągnąć Vmax, maksymalną szybkość reakcji, i wymagałaby do tego więcej substratu, ponieważ musi być wystarczająca ilość substratu, aby konsekwentnie konkurować z inhibitorem o dostęp do miejsc aktywnych.
Z drugiej strony, niekompetycyjny inhibitor nie pozwoliłby na osiągnięcie Vmax, ponieważ liczba enzymów dostępnych do wiązania jest zmniejszona.

Goh, Ee Teng i Marsha Y. Morgan. "Farmakoterapia uzależnienia od alkoholu – dlaczego, co i dlaczego." Farmakologia Pokarmowa i Terapia 45, nr 7 (2017): 865-882. [<a href="https://doi.org/10.1111/apt.13965">Źródło</a>]

inhibicja enzymów

Enzyme Inhibition

Inhibitory to cząsteczki, które zmniejszają aktywność enzymu poprzez wiązanie się z enzymem. W normalnie funkcjonującej komórce enzymy są regulowane przez różne inhibitory. Leki i inne toksyny mogą również hamować enzymy. Niektóre inhibitory wiążą się z miejscem aktywnym enzymu, podczas gdy inne hamują aktywność enzymatyczną, wiążąc się z innymi miejscami w strukturze białka.

Inhibitory konkurencyjne zajmują miejsce aktywne enzymów, przez co nie są one w stanie przyjąć substratu. Jednakże wystarczająco wysokie stężenia substratu mogą pokonać inhibitor; w rezultacie inhibitory konkurencyjne spowalniają początkową szybkość reakcji enzymów, ale nie wpływają na maksymalną szybkość enzymu. Jednym z przykładów inhibitora kompetycyjnego jest disulfiram, stosowany w leczeniu przewlekłego alkoholizmu. Po spożyciu alkohol jest zwykle przekształcany do aldehydu octowego, który następnie jest przekształcany do acetylokoenzymu A przez dehydrogenazę aldehydu octowego. Disulfiram wiąże się i zajmuje miejsce aktywne dehydrogenazy aldehydu octowego, uniemożliwiając enzymowi przeprowadzenie tej konwersji. W rezultacie pacjent przyjmujący disulfiram natychmiast zaczyna odczuwać objawy przypominające kaca, takie jak ból głowy, co zmniejsza spożycie alkoholu.

Inhibitory niekonkurencyjne wiążą się z odrębnymi miejscami enzymu, z dala od miejsca aktywnego. Nazywa się je miejscami allosterycznymi i kiedy cząsteczki się z nimi wiążą, kształt miejsca aktywnego zmienia się w taki sposób, że enzym ma mniejsze powinowactwo do substratu. Ponieważ niekonkurencyjne inhibitory nie zajmują miejsca aktywnego, obecność dodatkowego substratu nie jest w stanie przezwyciężyć niekonkurencyjnego hamowania, a enzym nie jest w stanie osiągnąć maksymalnej szybkości reakcji.

Wiązanie kowalencyjne pomiędzy inhibitorem a enzymem jest zwykle nieodwracalne, jak w przypadku niektórych toksyn. Większość inhibitorów regulatorowych normalnie aktywnych w komórce oddziałuje z enzymami poprzez słabe interakcje. Ten typ wiązania jest odwracalny i przydatny do regulacji procesów metabolicznych. Aktywnym obszarem badań jest poszukiwanie nowych cząsteczek, które mogą konkurencyjnie i niekonkurencyjnie hamować enzymy regulujące wzrost komórek w nowotworach.

Inhibicja enzymów

Inhibitory to cząsteczki, które zmniejszają aktywność enzymu poprzez wiązanie się z enzymem. W normalnie funkcjonującej komórce enzymy są regulowane przez różne ...

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competitive vs noncompetitive inhibitors

Enzyme inhibitors are molecules that reduce enzyme activity by binding to enzymes. Cells use these inhibitors to help regulate normal enzyme function. Drugs and toxins can also block enzymes and change how they work.

Some inhibitors bind at the active site, which is the part of the enzyme where the substrate normally fits. Competitive inhibitors do this by occupying the active site and preventing the substrate from binding. If the substrate concentration becomes high enough, it can outcompete the inhibitor. For that reason, competitive inhibitors slow the initial reaction rate but do not change the enzyme’s maximum rate.

A clear example is disulfiram, a drug used to treat chronic alcoholism. Alcohol is normally converted to acetaldehyde and then to acetyl coenzyme A by acetaldehyde dehydrogenase. Disulfiram binds to the active site of acetaldehyde dehydrogenase and blocks this conversion. This causes hangover-like symptoms, such as headache, and helps decrease alcohol consumption.

Noncompetitive inhibitors bind at a different part of the enzyme. These binding sites are called allosteric sites. When a noncompetitive inhibitor binds, it changes the shape of the active site and lowers the enzyme’s affinity for the substrate. Extra substrate cannot overcome this effect, so the enzyme cannot reach its maximum reaction rate.

Some inhibitors form covalent bonds with enzymes. This binding is usually irreversible, as with some toxins. Most inhibitors that regulate metabolism in cells bind more weakly. That weak binding is reversible and helps control metabolic processes. Researchers also study enzyme inhibitors as possible treatments for cancers that involve cell growth.

Competitive vs Noncompetitive Inhibitors

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enzyme inhibition

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key terms and concepts

Compare competitive and noncompetitive enzyme inhibitors, including active-site binding, allosteric effects, disulfiram, and how inhibitors regulate cells.

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Competitive vs Noncompetitive Inhibitors

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