Kinetic and structural characterization of interaction between trypsin and Equisetum arvense extract

Abstract

Kinetic and structural characterization of interaction between trypsin and Equisetum arvense extract [Trypsin ve Equisetum arvense özütü arasındaki etkileşimin kinetik ve yapısal karakterizasyonu] ABSTRACT Objective: In this study the inhibitory effect of E. arvense extract on trypsin activity and the effect of trypsin on E. arvense extract were studied. In addition the nature of the interaction between the extract and trypsin was investigated. Methods: The inhibitory effect ethanol extract of E. arvense on trypsin activity was determined using trypsin enzyme assay. The structural effects of the extract-trypsin interaction for the extract were analyzed by FTIR. Finally, the HPLC analyses were carried out to analyze the individual components of the extract and the supernatant and soluble precipitate phases. Results: E. arvense extract was found to decrease total percent activity of trypsin to 5% in 24 hour at 24 °C. FTIR analyses indicated that the interaction between trypsin and E. arvense extract caused changes in the structure and hydrogen bonding behavior and composition of the extract proteins. These interactions also caused the extract lipids to accumulate in the insoluble precipitate phase. Most of the phenolics remained in the supernatant phase enhancing the inactivation of trypsin. However, the precipitated compounds were shown to be of apolar in nature as shown in the HPLC chromatograms. Conclusion:The methods that were used showed that the high phenolic content of E. arvense was the main reason for the inhibition of trypsin enzyme activity by denaturing the enzyme. of 1:20. The dry leafs particles were shaked in the solution for overnight at 300 rpm at 24 °C. After the centrifugation at 2000xg for 5 minutes the supernatant was collected into 50 ml falcon tubes. The alcohol in the liquid phase was evaporated with a rotary evaporator. The aqueous extract was frozen for 24 hours and then freeze dried in a lyophilizer (Telstar-Cryodos). Preparation of inhibition solutionE. arvense extract was dissolved in distilled water to a final concentration of 10 mg/ml. By serial dilutions of stock solution 2 mg/ml, 0.2 mg/ml and 0.02 mg/ml concentrations were prepared. Preparation of trypsin solutionBovine pancreatic trypsin was purchased from Fluka Analytical (cat.93610) and used without further purification. Lyophilized powder of bovine pancreatic trypsin (Fluka Analytical, USA) was dissolved in 1 mM HCl to a final concentration of 0.1 mg/ml. Determination of enzyme kineticsTrypsin catalyzes the hydrolysis of N-benzoyl-L-arginine ethyl ester (BAEE) to N-benzoyl-L-arginine (BA) and ethanol. The slope of the absorbance versus time graph was the production rate of BA at pH 7.6.The reaction was held in a total volume of 3.2 ml quartz cuvette at 25 °C. The unit of trypsin activity was previously determined as 1 µmol BA produced per minute at 253 nm, at pH 7.6 and 25 °C. The reaction was carried out in 100 mM Tris buffer solution. To determine absorption of blank solution, 3050 μl tris buffer and 150 μl of BAEE solution ...