Evaluation of oxidative activity of horseradish peroxidase in thepresence of zinc ion; spectroscopic and molecular docking study

Aim and Zinc is one of the metals that preserve the structure and function of many tissues in the body. Its effect is concentration-dependent. It can disrupt the vital process of cellular respiration. This study is aimed to investigate the interaction of this metal in the function and structure of peroxidase as one of the most important oxidoreductase enzymes in cellular respiration process, experimentally and theoretically.
Material and In order to extract kinetic parameters using UV-visible spectroscopy techniques and molecular docking modeling, horseradish peroxidase activities were plotted against time and various concentrations of zinc. Absorbance spectrum of the enzyme was obtained in the presence and absence of zinc, to determine the structural change, which are responsible for enzyme inhibition..
The results showed that Zn2 strongly inhibited peroxidase activity in a reversible uncompetitive-noncompetitive pattern with IC50 370 μM. Moreover, Zn2 enhanced the lag time and decreased steady state rate of the enzyme. UV-visible spectrum and molecular docking analysis indicated that Zn2 binding site is distinct from the active site and transformational change and reduction of electron transfer ability of porphyrin ring were occurred in the presence of Zn2. .
We propose that excess amount of zinc induces inhibition in peroxidase activity and possibly causes disorder in cellular respiration and electron transport. It is also believed that it could be useful in drug design for cancer cells.