Name: substrate effects on enzyme rates
Uploaded: 2019-08-01T09:12:17.000Z
Duration: 1 min 19 s
Channel: JoVE

Hücre içinde, sübstrat konsantrasyonu gibi farklı çevresel şartlar enzimlerin kimyasal reaksiyonları katalize ettikleri oranı etkileyebilir.
 Enzim kinetiği adlandırılan bu süreç grafik olarak gösterilebilir.
 Reaksiyon oranı y ekseninde, bu örnekte sübstrat konsantrasyonu olan değişken şartlar ise x ekseninde gösterilir.
Reaksiyon hızı, ürünün oluşum hızıdır, ve V maks olarak tanımlanan maksimum hıza ulaşabilir, ve tüm mevcut enzimler sübstratlara iliştiğinde yatay seyre geçer.
 Bu nedenle reaksiyon hızı, bağlanmaya hazır bulunan enzimlerin konsantrasyonuyla sınırlıdır.
 Bu grafik ayrıca reaksiyon hızının artış hızını da gösterebilir.
Bu değişken km olarak gösterilir.
 Sübstrat konsantrasyonu V maks'ın yarısıdır ve enzimin sübstrat ile birleşme eğilimini veya çekim kuvvetini temsil eder.
 Düşük km'li bir enzimin birleşme eğilimi yüksektir çünkü maksimum reaksiyon hızına düşük sübstrat konsantrasyonunda ulaşır.
Aynı şekilde, yüksek km, düşük birleşme eğilimine denk gelir çünkü enzimin reaksiyon hızını maksimuma eriştirmesi için sübstrat konsantrasyonunun daha yüksek olması gereklidir.

Johnson, Kenneth A. "Yüzyıllık Enzim Kinetik Analizi, 1913'ten 2013'e." FEBS Mektupları 587, no. 17 (2 Eylül 2013): 2753–66. [<a href="https://doi.org/10.1016/j.febslet.2013.07.012">Kaynak</a>]
Suarez, R.K., J.F. Staples, J.R.B. Lighton ve T.G. West. "Enzimatik Akı Kapasiteleri ve Metabolik Akı Hızları Arasındaki İlişkiler: Kas Glikolizinde Dengesizlik Reaksiyonları." Amerika Birleşik Devletleri Ulusal Bilimler Akademisi Bildirileri 94, no. 13 (24 Haziran 1997): 7065–69. [<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC21285/." >Kaynak</a>]

enzim kinetiği

Enzyme Kinetics

Enzimler, reaktanların aktivasyon enerjisini düşürerek reaksiyonları hızlandırır. Enzimin reaktanları ürünlere dönüştürme hızına reaksiyon hızı denir. Mevcut reaktanların sayısı dahil olmak üzere çeşitli faktörler reaksiyon hızını etkiler. Enzim kinetiği, bir enzimin reaksiyon hızını nasıl değiştirdiğinin incelenmesidir.

Bilim adamları tipik olarak, bir test tüpünün kontrollü ortamında sabit miktarda enzimle enzim kinetiğini inceler. Sabit miktarda enzime daha fazla reaktan veya substrat eklendiğinde, enzim daha fazla ürün üretebildikçe reaksiyon hızı artar. Sonuç olarak, reaksiyon hızı substrat konsantrasyonuna göre grafiğe döküldüğünde, substratın arttırılması reaksiyon hızını artırır. Bununla birlikte, enzimin tüm aktif bölgeleri işgal edildiğinde, reaksiyon hızı düzleşir. Maksimum reaksiyon hızına ulaşılan substrat konsantrasyonuna V max denir. Mevcut enzim moleküllerinin sayısı V max 'ı sınırlar. Enzim miktarı artırılırsa, V max artar, ancak daha fazla substrat eklemenin bir etkisi olmaz.

Substrat konsantrasyonuna karşı reaksiyon hızının grafiği, bir enzimin kinetiğinin diğer önemli özelliklerini ortaya çıkarabilir. Reaksiyon hızının yarı yarıya V max (yani ½ V max ) olduğu substrat konsantrasyonuna Michaelis sabiti (K m ) denir. K m , bir enzim ve bir substrat arasındaki afinitenin bir temsilidir. Daha düşük bir K m içeren enzimler, V max 'a ulaşmak için daha az substrat gerektirir ve bu nedenle substratları için daha yüksek bir afiniteye sahiptir. İlginç bir şekilde, birçok enzim için K m değeri, substratın hücresel konsantrasyonuna çok yakındır. K m civarında, substrat konsantrasyonundaki küçük değişiklikler reaksiyon hızını önemli ölçüde etkileyebilir, bu nedenle hücresel substrat mevcudiyetindeki küçük değişiklikler tüm biyolojik yolun işlevini etkileyebilir.

Tüm enzimler, Michaelis Menten kinetiği olarak bilinen hiperbolik şekilli substrat hız grafiğini oluşturmaz. Michaelis Menten kinetiği, enzimin tek bir substratı katalize ettiğini varsayar. Allosterik olarak düzenlenen enzimler, birden fazla aktif bölgeye sahiptir ve reaksiyon hızı, substrat konsantrasyonuna göre grafiğe dönüştürüldüğünde sigmoid şekilli bir grafik üretme eğilimindedir.

Enzim kinetiği

Enzimler, reaktanların aktivasyon enerjisini düşürerek reaksiyonları hızlandırır. Enzimin reaktanları ürünlere dönüştürme hızına ...

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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 more product. If the reaction rate is graphed against substrate concentration, the curve rises as substrate increases.

The rate does not keep rising forever. Once all of the enzyme's active sites are occupied, the reaction rate levels off. The substrate concentration at which the maximum rate is reached is called V max. V max is limited by the number of enzyme molecules present. If more enzyme is added, V max increases, but more substrate alone has no further effect.

A rate-versus-substrate graph can also show other features of enzyme behavior. The substrate concentration at which the reaction rate is halfway to V max is called the Michaelis constant, or K m. K m shows the affinity between an enzyme and its substrate. A lower K m means less substrate is needed to reach V max, so the enzyme has a higher affinity.

For many enzymes, K m is close to the substrate concentration in cells. Near K m, even small changes in substrate concentration can strongly affect the reaction rate. That means small shifts in cellular substrate availability can influence the activity of an entire biological pathway.

Not all enzymes follow Michaelis Menten kinetics. This model assumes that an enzyme acts on a single substrate. Enzymes regulated allosterically have multiple active sites and usually produce a sigmoid-shaped graph instead of a hyperbolic one when reaction rate is plotted against substrate concentration.

Substrate Effects on Enzyme Rates

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key terms and concepts

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Substrate Effects on Enzyme Rates

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