The effect of cold atmospheric plasma treatment on the aggregation and conformational change of pepsin and alpha-chymotrypsin under physiological pH condition

Pepsin and alpha-chymotrypsin (ACT) are two common proteolytic enzymes responsible for the quality degradation in seafood postmortem. Cold atmospheric plasma (CAP) is a new non-thermal technology for maintaining and improving food quality. The conformation and structural behavior of pepsin and ACT induced by potentially denaturing CAP were investigated through various spectrofluorometric assays. Circular dichroism (CD) spectra indicated that the secondary structure of pepsin and ACT were significantly changed (p < 0.05), and spectrofluorometric assays on surface hydrophobicity, fluorescence emission, and fluorescence quenching constants indicated remarkable but varied tertiary structure alterations after treatment. The activities of pepsin and ACT decreased by 95.2% and 92.1% after CAP treatment. Phase diagram plots indicated that structural and conformational dynamics of pepsin and ACT were all-or-none processes leading to inactivation, and strongly indicated protein unfolding upon CAP treatment.