Catalytic activity and Conformaitonal stability of polyphenol oxidase in variousphysical states and concentrations under high pressure freezing

This study investigates the effects of high-pressure freezing (HPF) at 0.1–400 MPa and -20oC for 30 min on polyphenol oxidase (PPO) in both solid crystal (S-PPO) and liquid forms at high and low concentrations (HL/LL-PPO). The effects were ranked according to enzyme activity and structural changes in the following order: physical state > concentration > pressure > crystallization path. Notably, LL-PPO exhibited greater stability than both HL-PPO and S-PPO, under HPF conditions, low temperatures provide a protective effect against the pressure-induced denaturation of S-PPO. Additionally, the sulfhydryl content and the high concentration state are crucial for maintaining the structural stability of L-PPO. By altering the physical state of PPO (Liquid and Solid), the enzyme's activity can be effectively regulated through activation and inhibition. Furthermore, the back propagation artificial neural network model demonstrates a precise fit for the correlation between spatial structure and enzyme activity.