Effects of electrolytes on the enzymatic activity in urea/ureasesystem
Başlık çevirisi mevcut değil.
- Tez No: 770526
- Danışmanlar: PROF. PİERANDREA LO NOSTRO
- Tez Türü: Yüksek Lisans
- Konular: Moleküler Tıp, Molecular Medicine
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2021
- Dil: İngilizce
- Üniversite: Università degli Studi di Firenze
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 53
Özet
Urease is involved in many natural processes, spanning from the nitrogen cycle to pathologies. For example, Helicobacter pylori exploit urease to buffer the acidic pH of animals' stomach, causing severe health problems to the host, like ulcers and tumors. Furthermore, in non-buffered solutions, urease has a pH dependence that can be used to induce clock-type reactions. Finding biocompatible and controllable inhibition mechanisms may offer new possibilities in the manipulation and design of medical and environmental applications through the modulation of the enzyme activity. In this project, we investigate the specific ion effect on the enzymatic activity of urease. These effects emerge at moderate to high concentrations of electrolytes in solutions and cause many physicochemical parameters of the solutions to deviate from the ideal trend. Also, electrolyte presences influence numerous parameters of the proteins including their solubility, stability, aggregation, and conformation. We studied the effect of anions in the Hofmeister series employing the potassium salts of H2PO4 - , ClO3 - , BrO3 - , IO3 - , Cl- , Br- , NO3 - , I- , ClO4 - , SCN- . To establish a relation between the enzymatic activity and the added electrolytes, we investigated the enzymatic hydrolysis of urea in unbuffered media, in the presence and the absence of salts. In these conditions, the pH variation in time follows an autocatalytic behavior described by an S-type curve. The time lag between the beginning of the reaction (mixing time, t = 0) and the maximum rate during the autocatalysis (inflection point of the S-shape curve) is called clock time and it was chosen as the benchmark parameter to compare different systems. Typical pH profiles of the blank consist of an initial slow increase of the pH with the consequent increase in rate towards pH 7 (autocatalysis). This increase is then rapidly slowed down at still increasing pH and reaches a plateau around pH 9.2. The clock reactions were performed under magnetic stirring and were kept at 25° C. Explored absolute values of the clock time for the different conditions were normalized with respect to the daily blank. To have an estimation of the speed of the process (∆pH/∆t), the derivatives of the pH changes as a function of time were also calculated for each curve. The normalized differences in the clock time and the maximum speed were compared. Finally, a Jones-Dole fashion treatment of the obtained data was employed to calculate ion-specific B coefficients. The results clearly show that the electrostatic regime dominates at 10-3 M (10-4 M for H2PO4 - and IO3 - ) but at higher concentrations of electrolytes the regime is dominated by specific ion effects and the activity of the enzyme deviates from ideality depending on the nature of the added ion. The most prominent salt effect is the increase of the clock time and the decrease of the maximum rate velocity during the enzymatic reaction. However, the addition of salts did not change the final pH. These effects can represent an interesting option for the treatment of Helicobacter pylori. Furthermore, some of the ions analyzed are not harmful to humans and the concentration needed is lower than the concentration of electrolytes in the mammals' blood, about 0.17 M. Also, these effects can be used in the stabilization of urease, including the adjustment of its clock time even in buffered conditions where the pH modification is not possible for the clock adjustments.
Özet (Çeviri)
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