The oxidation process, catalyzed by the peroxidase enzymes, occurs in all domains of life to detoxify the hydrogen peroxide toxicity. The most well-known, applicable and vastly studied member of the peroxidases family is horseradish peroxidase (HRP), especially the isoenzyme C (HRP C). HRP (primarily HRP C) is commercially available and applicable in biotechnology and diagnosis. Recently, a novel application of HRP has been introduced in cancer therapy as the combination of HRP with indole-3-acetic acid (IAA). The anticancer activity of HRP/IAA complex is through oxidation of IAA by HRP in hypoxic tumor condition, which leads to apoptosis and cancerous cell death. However, the molecular interaction of HRP/IAA has not been elucidated. Identifying the interaction of IAA with HRP would provide a better insight into its function and applications. In this study, molecular docking and molecular dynamics (MD) simulation were applied to determine the molecular interaction of the IAA/HRP complex. The docking study represented that IAA bound at the 'exposed' heme edge of the HRP enzyme, and the IAA entrance to the enzyme was situated at the carboxymethyl side-chain of the selected structure. Our computational results showed the HRP/IAA complex structure stability. While hydrogen bond formation with ARG38 and HIS42 stabilized the substrate, hydrophobic interactions with Phe68, Gly69, Leu138, Pro139, Pro141 and Phe179 contributed to IAA/HRP complex stability. The results can help to better understand peroxidase enzyme activity and would pave the way for future development of new therapeutics with improved anticancer efficacy.Communicated by Ramaswamy H. Sarma.
Keywords: Horseradish peroxidase; bioinformatics; indole-3-acetic acid; molecular docking; molecular dynamics simulation.