Determination of the initial rate of enzymatic reactions in soils

Öz

The enzymatic activity of the soil can be used as a diagnostic indicator of soil fertility and quality. In order to understand this feature of enzymes, the kinetics of enzymes should be examined. As is known, the practical determination of the reaction rate in kinetic studies is carried out on the basis of determining the initial rate of the enzymatic reaction.In the study, analysis were conducted with different concentrations (3, 6, 9, 12, 15, 18, 21, 24, 30 %) of H2O2 to calculate kinetic parameters (Vmax, KM, Vmax/KM, KSEE, [S]opt ve υ0,max) of catalase enzyme to calculate the kinetic parameters of the soil catalase enzyme (Vmax, KM, Vmax/KM, KSEE, [S]opt and υ0,max). In this regard, first the values for velocity (υ) were calculated by using the analysis results. Then, different models expressing the relation product – substrate: [P]=f([S]) were determined. Based the model selection criteria (R2, R2adj, σ, A, D, UII, AIC), the most proper model showing the relation [P]=f([S]) was determined. Initial velocity was calculated with the formula υ0=d([P])/dt│t=0 using the selected model. All calculations in the study were made with the STATISTICA-10 package program. Results showed that, it was determined that as the substrate (H2O2) concentration increased, the product (O2) decreased, and it was also observed that the substrate inhibited the catalase enzyme reaction. In order to determine the initial velocity, it was found that the most suitable model according to the model selection criteria was Binomial-1. The kinetic parameters were calculated using the initial rate values according to low and high concentration values of the substrate. In addition, the highest initial velocity (υ0,max =5.3508 ml O2/1 min 5g soil) was reached at the optimum value of the substrate (12.2957 %).

Anahtar Kelimeler

• Soil
• enzyme
• catalase
• kinetic parameters
• initial rate

Topraklarda enzimatik reaksiyonların başlangıç hızının belirlenmesi

Öz

Toprağın enzimatik aktivitesi, toprakların verimliliğinin, kalitesinin tanısal bir göstergesi olarak kullanılabilir. Enzimlerin bu özelliğinin anlamlandırılması için enzimlerin kinetiğinin incelenmesi gerekmektedir. Bilindiği gibi, kinetik araştırmalarda reaksiyon hızının pratik olarak tespit edilmesi, enzimatik reaksiyonun başlangıç hızının belirlenmesi temelinde gerçekleştirilir. Çalışmada, toprağın katalaz enziminin kinetik parametrelerini (Vmax, KM, Vmax/KM, KSEE, [S]opt ve υ0,max) hesaplamak için H2O2 substratının farklı konsantrasyonlarında (3, 6, 9, 12, 15, 18, 21, 24, 30 %) analizler yapılmıştır. Bu parametrelerin hesaplanması için analiz sonuçları kullanılarak önce hız (υ) değerleri hesaplanmıştır. Sonra ürün – substrat: [P]=f([S]) bağıntısını ifade eden farklı modeller belirlenmiştir. Daha sonra model seçim kriterlerine (R2, R2adj, σ, A, D, UII, AIC) göre [P]=f([S]) bağıntısını yansıtan en uygun model belirlenmiştir. Belirlenen modele göre başlangıç hız: υ0=d([P])/dt│t=0 formulü ile hesaplanmıştır. Çalışmadaki tüm hesaplamalar STATISTICA-10 paket programı ile yapılmıştır. Araştırma sonuçlarında; substrat (H2O2) konsantrasyonu arttıkça, ürünün (O2’nin) azaldığı tespit edilmiş, substratın katalaz enzim reaksiyonunu engellediği (inhibe ettiği) gözlenmiştir. Başlangıç hızın belirlenmesi için, model seçim ölçütlerine göre en uygun modelin Binom-1 olduğu bulunmuştur. Substratın düşük ve yüksek konsantrasyon değerlerine karşılık gelen başlangıç hız değerleri kullanılarak kinetik parametreler hesaplanmıştır. Ayrıca, substratın optimum değerinde (12.2957 %) en yüksek başlangıç hıza (υ0,max =5.3508 ml O2/1 dak 5g toprak) ulaşılmıştır.

Anahtar Kelimeler

• Toprak
• enzim
• katalaz
• kinetik parametreler
• başlangıç hız.

Kaynakça

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