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

Spezifische Chemikalien steuern die Wirkung von Enzymen, durch Hemmung oder Blockierung ihrer Funktion.
 Enzymhemmer gibt es in zwei verschiedenen Formen, konkurrierend und nicht konkurrierend.
 Ein konkurrierender Hemmer ist dem spezifischen Substrat des Enzyms so ähnlich, dass er an die aktive Stelle binden kann und das Substrat von der Bindung abhält.
 Diese Aktion verringert die Zahl der Enzyme erheblich, die für die Bindung an das Substrat zur Verfügung stehen.
 Im Gegensatz dazu bindet ein nicht konkurrierender Hemmer sich von der aktiven Stelle weg, beeinflusst sie aber, indem er z.
 B.
 die Form des Enzyms ändert und die Affinität für die Substratbindung an die aktive Stelle stark reduziert und verhindert, dass das Enzym ordnungsgemäß funktioniert.
 Darüber hinaus beeinflussen beide Inhibitortypen die Geschwindigkeit einer chemischen Reaktion unterschiedlich.
 Im Vergleich zu einer Kontrolle, einer normalen enzymatischen Reaktionsgeschwindigkeit, würde eine Reaktion mit einem konkurrierenden Hemmer länger dauern, um v max, die maximale Reaktionsgeschwindigkeit, zu erreichen, und würde mehr Substrat erfordern, um dies zu tun, da es genügend Substrat geben muss, um den Hemmer konsequent um den Zugang zu den aktiven Stellen zu übertreffen.
 Andererseits würde ein nicht konkurrierender Inhibitor nicht zulassen, dass die Rate v max erreicht, da die Anzahl der für die Bindung verfügbaren Enzyme reduziert wird.

Goh, Ee Teng und Marsha Y. Morgan. "Pharmakotherapie bei Alkoholabhängigkeit – das Warum, das Was und das Warum." Alimentary Pharmacology & Therapeutics 45, Nr. 7 (2017): 865-882. [<a href="https://doi.org/10.1111/apt.13965">Quelle</a>]

enzymhemmung

Enzyme Inhibition

Inhibitoren sind Moleküle, welche die Enzymaktivität durch die Bindung des Enzyms hemmen. In einer normal funktionierenden Zelle werden die Enzyme durch eine Vielzahl von Inhibitoren reguliert. Auch Medikamente und andere Toxine können Enzyme hemmen. Einige Inhibitoren binden an das aktive Zentrum des Enzyms, während andere die Enzymaktivität durch Bindung an andere Stellen der Proteinstruktur verhindern.
 
 Kompetitive Inhibitoren besetzen das aktive Zentrum von Enzymen, wodurch diese nicht in der Lage sind, das Substrat aufzunehmen. Jedoch können ausreichend hohe Konzentrationen des Substrats den Inhibitor verdrängen. Daher verlangsamen kompetitive Inhibitoren die anfängliche Reaktionsgeschwindigkeit von Enzymen, aber beeinträchtigen nicht die maximale Geschwindigkeit von Enzyme. Ein Beispiel für einen kompetitiven Inhibitor ist das Medikament Disulfiram. Es wird zur Behandlung von chronischer Alkoholabhängigkeit eingesetzt. Bei der Einnahme von Alkohol wird dieser normalerweise in Acetaldehyd umgewandelt, welcher dann von der Acetaldehyd-Dehydrogenase in Acetyl-Coenzym A umgewandelt wird. Disulfiram bindet sich an die Acetaldehyd-Dehydrogenase und blockiert ihr aktives Zentrum, so dass das Enzym nicht mehr in der Lage ist, diese Umwandlung durchzuführen. Infolgedessen treten bei einem Patienten, der Disulfiram einnimmt, sofort katerähnliche Symptome wie Kopfschmerzen auf, was zu einem verringerten Alkoholkonsum führt.
 
 Nicht-kompetitive Inhibitoren binden an verschiedene Regionen des Enzyms, die vom aktiven Zentrum entfernt sind. Man nennt diese Bereiche allosterische Regionen. Wenn diese durch Moleküle gebunden werden, wird die Form der aktiven Stelle so verändert, dass das Enzym eine geringere Affinität zum Substrat hat. Da nicht-kompetitive Inhibitoren das aktive Zentrum nicht besetzen, kann das Vorhandensein von zusätzlichem Substrat, die nicht-kompetitive Inhibition nicht überwinden und das Enzym kann seine maximale Reaktionsgeschwindigkeit nicht erreichen.
 
 Eine kovalente Bindung zwischen einem Inhibitor und einem Enzym ist in der Regel irreversibel, wie bei einigen Toxinen. Die meisten regulatorischen Inhibitoren, die normalerweise in der Zelle aktiv sind, interagieren mit den Enzymen durch schwache Wechselwirkungen. Diese Art der Bindung ist reversibel und nützlich für die Regulierung von Stoffwechselprozessen. Die Erforschung neuer Moleküle zur kompetitiven und nicht-kompetitiven Hemmung von Enzymen, die das Zellwachstum bei Krebs regulieren, ist ein aktives Forschungsgebiet.

Enzymhemmung

Inhibitoren sind Moleküle, die die Enzymaktivität reduzieren, indem sie an das Enzym binden. In einer normal funktionierenden Zelle werden Enzyme durch eine Vielzahl von ...

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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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allosteric regulation

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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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