Quench treatment cytochrome c: Transformation from a classical redox protein to a peroxidase like enzyme

Hemoproteins play important roles in physiological activities in animals and plants. The research on the structures and properties of hemoproteins can better understand the relationship between structure and function of hemoproteins and expand the application fields and scopes of hemoproteins. In this report, the peroxidase activity, stability and structure changes of cytochrome c (Cyt c) and quench treatment Cyt c at different pH values and different quenching temperatures were studied by UV–Vis spectroscopy, circular dichroism, Fourier transform infrared spectroscopy and electrochemical methods, respectively. The results indicated: 1. The optimal pH value and temperature for Cyt c quench treatment were pH 9 and 85 °C (marked as Q-Cyt c), respectively, in 50 mM sodium phosphate buffer solution (PBS). 2. The Michaelis–Menten constant K m , maximum catalytic rate V max and catalytic rate constant K cat of Q-Cyt c were calculated to be 3.8 μM, 0.42 μM·s −1 and 0.085 s −1 , respectively, in 50 mM pH 9 PBS. The catalytic efficiency of Q-Cyt c was 0.022 μM −1 s −1 , which was 30% of the catalytic efficiency of horseradish peroxidase (0.0742 μM −1 s −1 ). 3. Compared with natural Cyt c, while the overall structure of Q-Cyt c became looser, its hydrophobicity had changed. At the same time, the degree of exposure and hydrophobicity of the heme structure decreased, respectively. 4. The content of Random-Coil structure of Q-Cyt c would restore to its state at room temperature, while the other secondary structures maintained their structures at high temperature (below denaturation temperature) before quenching. 5. The formal potential of Q-Cyt c was greater than that of Cyt c, the hydrophobicity of Q-Cyt c was enhanced compared with Cyt c, which might lead to the decreased stability and improved catalytic activity of Q-Cyt c. 6. Q-Cyt c could be used in industrial decolorization and biosensor construction. 7. Quench treatment may be an effective method to transform Cyt c from a classical redox protein to a peroxidase like enzyme.