EPR spectroscopy of dog-rose polyphenoloxidase

Polyphenoloxidase(PPO) of dog-rose fruit was extracted and purified through $(NH_4)_2SO_4$ precipitation and dialysis. The optimum conditions for this purpose, i.e., pH and temperature, were determined with 4-methylcatechol optimum pH and temperature and found to be pH 8.5 and $20^\circ C$, respectively. The inhibition effect of ascorbic acid was investigated and the $I_{50}$ value was found to be $1.57\times10^{-4}$ M. The activity of dog-rose PPO was investigated by electron paramagnetic resonance (EPR) at different pH levels and temperatures. The optimum conditions obtained from both spectrophotometry and EPR were compared.