Abstract:

The effect of heat treatment on the relative activity of polyphenol oxidase (PPO) from mushroom was
investigated. The changes of secondary and tertiary structure of PPO after heat treatment at various temperatures (50, 55,
60 and 65 ℃) for 10 min were analyzed by circular dichroism (CD) spectroscopy and fluorescence emission spectroscopy.
The results showed that the relative activity of PPO decreased gradually with increasing treatment time at each investigated
temperature. CD spectral analysis also showed that the secondary structure of PPO was changed after the heat treatment,
which was reflected by a decrease of α-helix content and an increase of β-sheet content. However, no obvious difference was
observed for β-turn and random coil contents. Meanwhile, fluorescence emission spectral analysis showed that the tertiary
structure of PPO was changed after the heat treatment with an apparent red shift in the maximum peak wavelength.

Key words: polyphenoloxidase, heat treatment, secondary structure, tertiary structure