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

- [Eğitmen] Özel kimyasallar enzimlerin eylemini fonksiyonlarını önleyerek veya bloke ederek düzenleyebilir.
 Enzim önleyiciler iki farklı biçimdedir, rekabetçiler ve rekabetçi olmayanlar.
 Rekabetçi önleyici enzimin özel substratına yeterince benzer ve aktif bölgeye bağlanarak, substratın bağlanmasını bloke edebilir.
Bu eylem esasen substratı bağlamak için mevcut enzim sayısını azaltır.
 Bunun tersine rekabetçi olmayan önleyici, aktif bölgeden uzakta bağlanır ama yine de burayı etkiler, bunu da örneğin enzimin şeklini değiştirerek ve substratın aktif bölgeye bağlanma eğilimini büyük ölçüde azaltarak ve enzimin doğru çalışmasını önleyerek gerçekleştirir.
 Ayrıca, iki tip önleyici kimyasal reaksiyonun hızını farklı şekilde etkiler.
Kontrol tepkimesiyle kıyaslandığında, normal bir enzimatik tepkime hızı, yani, rekabetçi önleyici içeren bir tepkime, v max'a, yani maksimum tepkime hızına daha uzun sürede ulaşır ve bunun için daha fazla substrat gerekir, çünkü aktif bölgelere ulaşması içim önleyiciye sürekli üstünlük sağlamaya yetecek kadar substrat olmalıdır.
 Diğer yandan, rekabetçi olmayan bir önleyici hızın v max'a ulaşmasına izin vermez, çünkü bağlanma için mevcut enzim sayısı azalır.

Goh, Ee Teng ve Marsha Y. Morgan. "Alkol bağımlılığı için farmakoterapi - neden, ne ve neden." Sindirim Farmakolojisi ve Terapötikler 45, hayır. 7 (2017): 865-882. [<a href="https://doi.org/10.1111/apt.13965">Kaynak</a>]

enzim İnhibisyonu

Enzyme Inhibition

İnhibitörler, enzime bağlanarak enzim aktivitesini azaltan moleküllerdir. Normal işleyen bir hücrede, enzimler çeşitli inhibitörler tarafından düzenlenir. İlaçlar ve diğer toksinler de enzimleri inhibe edebilir. Bazı inhibitörler enzimin aktif bölgesine bağlanırken diğerleri protein yapısındaki diğer bölgelere bağlanarak enzimatik aktiviteyi inhibe eder.

Kompetitif inhibitörler, enzimlerin aktif bölgesini işgal ederek onları substrata uyum sağlayamaz hale getirir. Bununla birlikte, yeterince yüksek substrat konsantrasyonları, inhibitörden üstün olabilir; Sonuç olarak kompetitif inhibitörler, bir enzimin başlangıç reaksiyon hızını yavaşlatır, ancak enzimin maksimum oranını etkilemez. Kompetitif bir inhibitör örneği, kronik alkolizmi tedavi etmek için kullanılan ilaç disülfiramdır. Alkol yutulduğunda, normalde asetaldehite dönüştürülür ve bu daha sonra asetaldehit dehidrojenaz ile asetil koenzim A'ya dönüştürülür. Disülfiram, asetaldehit dehidrojenazın aktif bölgesine bağlanır ve burayı işgal ederek enzimi bu dönüşümü gerçekleştiremez hale getirir. Sonuç olarak, disülfiram alan bir hasta hemen baş ağrısı gibi akşamdan kalmaya benzer semptomlar yaşamaya başlar ve bu nedenle alkol tüketimini azaltır.

Kompetitif olmayan inhibitörler, enzim üzerinde aktif bölgeden uzakta farklı bölgelere bağlanır. Bunlara allosterik bölgeler denir ve moleküller bunlara bağlandığında, aktif bölgenin şekli, enzimin substrat için daha düşük bir afiniteye sahip olacağı şekilde değiştirilir. Kompetitif olmayan inhibitörler aktif bölgeyi işgal etmediğinden, ek substratın varlığı kompetitif olmayan inhibisyonun üstesinden gelemez ve enzim maksimum reaksiyon oranına ulaşamaz.

Bir inhibitör ile bir enzim arasındaki kovalent bağlanma, bazı toksinlerde olduğu gibi, genellikle geri döndürülemez. Hücrede normalde aktif olan çoğu düzenleyici inhibitör, zayıf etkileşimlerle enzimlerle etkileşime girer. Bu tür bir bağlanma tersine çevrilebilir ve metabolik süreçlerin düzenlenmesi için kullanışlıdır. Kanserde hücre büyümesini düzenleyen enzimleri kompetitif ve kompetitif olmayan bir şekilde engellemek için yeni moleküllerin keşfi aktif bir araştırma alanıdır.

Enzim İnhibisyonu

İnhibitörler, enzime bağlanarak enzim aktivitesini azaltan moleküllerdir. Normal olarak işleyen bir hücrede, enzimler çeşitli ...

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KEY TERMS AND CONCEPTS

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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

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...

first law of thermodynamics

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Energy flow in a food web shows the First Law of Thermodynamics in action. Energy cannot be created or destroyed. It can only change form as it moves through living things and the environment. Sunlight is the starting point. Plants capture radiant energy from the sun during photosynthesis and turn it into chemical energy stored in complex carbohydrates. At the same time, oxygen is released into the atmosphere. Herbivores eat the plants and use those sugars during digestion. The energy is...

second law of thermodynamics

Entropy in Food Web Energy Flow

The Second Law of Thermodynamics explains why entropy increases as energy moves through a system. Entropy means the amount of disorder in a system. Each time energy is transferred or transformed, some energy is lost as unusable heat. That heat can raise the motion of nearby molecules for a short time and make the surroundings less ordered and more random. This idea also appears in a food web. Primary producers, such as plants, take in energy from the sun and make food. During this process,...

kinetic energy

Motion as a Source of Energy

Kinetic energy is the energy of motion. It appears when an object is moving and can do work or cause change. A waterfall is one clear example. Water behind a dam has potential energy, but when it rushes downward, that moving water has kinetic energy. When the water reaches the bottom and stops moving, its energy can become potential energy again. Kinetic energy also shows up in living systems. Plants absorb light particles, called photons, which move very fast and help create chemical energy...

potential energy

Stored Energy in Motion and Bonds

Stored energy in motion and bonds is called potential energy. It depends on the structure of an object or the position of matter in space. Raising a kettlebell changes its location and increases its potential energy. A stretched rubber band also stores potential energy, which can later change into kinetic energy. Chemical bonds between atoms hold another form of stored energy called chemical energy. These bonds involve attractive forces, and that energy can change into other forms during a...

free energy

Gibbs Free Energy in Chemical Reactions

Gibbs free energy is a measure of useful energy that can be taken from a chemical reaction to do work. It is written as G and named for scientist Gibbs, who discovered it. This energy is what remains after entropy is considered. A reaction can either take in energy or release it. Reactions that absorb energy are called endergonic reactions. Reactions that release energy are called exergonic reactions. The direction of energy flow helps show which type of reaction is happening. Plants carry...

activation energy

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Activation energy is the minimum energy a chemical reaction needs to keep going. When the activation energy is higher, the reaction usually happens more slowly. Adding heat can speed the reaction because molecules move faster and collide more often. As reactants collide, bonds break and the reaction moves through an uphill phase. That step creates the transition state, which is an unstable, high-energy state of the reactants. After that, new bonds form, products appear, and free energy is...

hydrolysis of atp

ATP Breakdown and Energy Release

ATP breakdown releases energy for cell work. Adenosine triphosphate, or ATP, can lose one or two phosphate groups when water is added. This hydrolysis reaction is exergonic, which means it releases energy that the cell can use. When one phosphate group is removed, ATP becomes ADP, or adenosine diphosphate. Inorganic phosphate is also released. ADP can then be hydrolyzed again to form AMP, or adenosine monophosphate, after a second phosphate group is removed. ATP has a clear structure. It is...

phosphorylation

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Phosphorylation helps control how proteins work in cells. It is the addition or removal of phosphate groups, and it is the most common chemical change that regulates cellular processes. These changes can alter a protein’s structure, activity, stability, location inside the cell, and interactions with other proteins. During phosphorylation, protein kinases move the terminal phosphate group from ATP to a specific amino acid side chain on a target protein. The amino acids most often...

induced-fit model

How Enzymes Adjust to Their Substrates

Enzymes speed up many chemical reactions in cells. They are biological catalysts, so they increase reaction speed without being consumed or permanently changed. They do this by lowering the activation energy needed to turn reactants into products. Enzymes are proteins that usually work by binding to a substrate, which is the reactant molecule they act on. They show substrate specificity, meaning they bind only certain substrates. This specificity depends mainly on the shape and chemical...

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

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...

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 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...

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

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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