Intervention on activity and structure of cathepsin L during surimi gel degradation under microwave irradiation

Abstract

This study was aimed to investigate the effect of microwave heating (MWH) on the activity and conformation of cathepsin L (Cat L) compared to traditional conduction heating during surimi gel degradation stage. The gel properties and SDS-PAGE analysis showed that hydrolysis of myosin heavy chain was prevented by microwave. The activity of Cat L was affected by microwave power and heating time, which inhibited by MWH mainly due to the changes of conductivity caused by the vibration of polar groups under MWH. In addition, the reduction of total sulfhydryl group of Cat L during microwave irradiation led to conformation changes of Cat L. Significant decrease (P < 0.05) in α-helix of Cat L was found using circular dichroism, revealing that MWH altered the secondary structure of Cat L. The molecular chain configuration of Cat L under microwave irradiation was characterized by Laser light scattering. The Rg/Rh of Cat L molecule increased first and then decreased, illustrating that the molecular structure of Cat L was curled up and active center was buried, which lead to the inhibition of Cat L.