Inactivation mechanism of polyphenol oxidase during ultrasound treatment

Baltacıoğlu, Hande
In this study, the activity and conformational changes of mushroom polyphenol oxidase (PPO) were investigated during the inactivation by heat-ultrasound treatment at different power, temperature and time combinations. The secondary structure change of the enzyme during inactivation was analyzed by using Fourier Transform Infrared (FTIR) spectroscopy and compared with the enzyme activity change. In thermosonication (TS) treatment, the residual enzyme activity decreased with increasing power, time and temperature. The enzyme inactivation higher than 99 % was obtained at 100 % amplitude at 60 °C for 10 min. For comparison, when the stability of mushroom PPO after thermal treatment was investigated, approximately 99% inactivation was obtained at 70 °C for 5 min. D value for thermal treatment at 60°C was found as 6.66 min whereas for 100, 80 and 60 % amplitude TS treatments at the same temperature, D values were found as 2.09, 3.33 and 3.44 min, respectively. FTIR studies showed that the thermal and TS treatments caused an irreversible change on the secondary structure of the enzyme. α-helix and β-sheet content decreased, while aggregated β-sheet, turns and random coil content increased during the temperature increase. The transition temperature (Tm) values of TS and thermal treatments were 44 and 55 ºC, respectively. This result showed that heat and ultrasound combination behaved synergistically on the conformational change of the enzyme. Compared to the thermal treatment, TS treatment seemed to be more effective on the secondary structural change at lower temperatures.


Secondary structure and conformational change of mushroom polyphenol oxidase during thermosonication treatment by using FTIR spectroscopy
Baltacıoğlu, Hande; Bayındırlı, Alev; Severcan, Feride (2017-01-01)
To understand the conformational changes of mushroom PPO, the secondary structural change of the enzyme during thermosonication treatment at different power (60, 80 and 100%), temperature (20-60 degrees C) and time (0-30 min) combinations was investigated by using FTIR spectroscopy and compared with the change in enzyme activity. The enzyme inactivation higher than 99% was obtained at 100% amplitude at 60 degrees C for 10 min. FTIR studies showed that marked spectral changes were noted after ultrasound trea...
Biophysical characterization of proteins in solution and human fluids for cancer diagnosis applications using fourier transform infrared spectroscopy
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Proteins play very important roles in cells regulation and structure. Understanding of proteins structures greatly help in understanding of the mechanism of action of these proteins. The optical spectroscopic techniques such as Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy can be used to study proteins in its native environment without complicated sample preparations that is required for a high resolution technique such as x-ray. In order to calculate the protein secondary struc...
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The objective of this presented study was to synthesize optically active compounds considered to be key intermediates in the synthesis of Oseltamivir (Tamiflu) by performing chemical and biotechnological methods. Thereof, the carboethoxy cyclohexenone skeleton first was synthesized utilizing easily available substances. The synthesis of alpha-hydroxy ketones in enantiomerically pure form offers a great importance in the synthesis of biologically active compounds. Toward this fact, the enantioselective synth...
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G-Protein Coupled Receptors (GPCRs) constitute a large family of receptors which act by sensing the molecules outside the cell and start a signal transduction inside the cell through interacting with their associated G-proteins. This interaction results in activation or repression of related signaling pathways via associated secondary messengers. Dopamine receptor D2 (D2R) is a member of D2-like Dopamine Receptor group, which also belongs to the GPCR family. It is known that D2R has critical roles in emotio...
Citation Formats
H. Baltacıoğlu, “Inactivation mechanism of polyphenol oxidase during ultrasound treatment,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.