Toxic mechanism of pyrene to catalase and protective effects of vitamin C: Studies at the molecular and cell levels.

Polycyclic aromatic hydrocarbons, distributing extensively in the soil, would potentially threaten the soil organisms (Eisenia fetida) by triggering oxidative stress. As a ubiquitous antioxidant enzyme, catalase can protect organisms from oxidative damage. To reveal the potential impact of polycyclic aromatic hydrocarbon pyrene (Pyr) on catalase (CAT) and the possible protective effect of Ascorbic acid (vitamin C), multi-spectral and molecular docking techniques were used to investigate the influence of structure and function of catalase by pyrene. Fluorescence and circular dichroism analysis showed that pyrene would induce the microenvironmental changes of CAT amino acid residues and increase the α-helix in the secondary structure. Molecular simulation results indicated that the main binding force of pyrene around the active center of CAT is hydrogen bonding force. Furthermore, pyrene inhibited catalase activity to 69.9% compared with the blank group, but the degree of inhibition was significantly weakened after vitamin C added into the research group. Cell level experiments showed that pyrene can increase the level of ROS in the body cavity cell of earthworms, and put the cells under the threat of potential oxidative damage. Antioxidants-vitamin C has a protective effect on catalase and maintains the stability of intracellular ROS levels to a certain extent.