Molecular interaction between 4-aminoantipyrine and catalase reveals a potentially toxic mechanism of the drug.

4-Aminoantipyrine (AAP) is scarcely administered as an analgesic drug because of the potential side effects. The residue of AAP in the environment possesses a potential threat to human health. In this article, the binding mode of AAP with the important antioxidant enzyme catalase (CAT) was investigated using spectroscopic and molecular docking methods. AAP can interact with CAT to form an AAP-CAT complex. The binding constant, number of binding sites and thermodynamic parameters were measured, which indicated that AAP could spontaneously bind with CAT through electrostatic forces with one binding site. Molecular docking results revealed that AAP bound into the CAT central cavity. UV-visible absorption, synchronous fluorescence and circular dichroism (CD) results provide data concerning conformational and some microenvironmental changes of CAT. Furthermore, the binding of AAP can inhibit CAT activity in erythrocytes. The present study provides direct evidence at a molecular level to show that exposure to AAP could induce changes in the enzyme CAT structure and function. The estimated methods in this work can be applied to characterize interactions of enzyme systems and other pollutants and drugs.