The effect of high pressure carbon dioxide on the inactivation kinetics and structural alteration of phenylalanine ammonia-lyase from Chinese water chestnut: An investigation using multi-spectroscopy and molecular docking methods

The effect of high pressure carbon dioxide (HPCD) on the inactivation kinetic and structure of phenylalanine ammonia-lyase (PAL) from Chinese water chestnut (CWC) was studied in this paper. The inactivation kinetic of PAL treated by HPCD (1–4 MPa, 35–55 °C, and 5–60 min) were determined and fitted to the first order kinetics model with calculating kinetic parameters. As revealed by the circular dichroism spectral, the α-helix and β-turn content in secondary structure increased and the β-sheet content decreased. And the intensity of the fluorescence spectra reflecting tertiary structure decreased, together with the λmax blue-shifted with the increasing pressure. Fluorescence and circular dichroism spectral results indicated that the conformation of PAL was altered by HPCD. The findings of particle size distribution and ζ potential showed that HPCD could cause the aggregates of PAL particles. Moreover, molecular docking indicated the interactions between small molecules (CO2, H2CO3, HCO3−, and CO32−) and PAL might result in a decrease in PAL activity by forming steric hindrance, preventing substrate from binding. Finally, this paper proposed a potential mechanism for inactivation of PAL by HPCD treatment, where the loss in PAL activity was correlated to changes in secondary and tertiary structure of PAL, which was induced by aggregation effect of HPCD.