Conserved acidic second shell residue modulates the structure, stability and activity of non-seleno human peroxiredoxin 6

1-Cys peroxiredoxin6 (Prdx6) is unique and inducible bifunctional enzyme in the mammalian lungs and plays a role in the progression and inhibition of cancerous cells at different stages. The enzyme possesses two distinct active sites for phospholipase A2 and peroxidase activity. The conserved residues surrounding the peroxidase active site, also called as second shell residues are Glu50, Leu71, Ser72, His79 and Arg155. Since there is no study done about the active site stabilization of the transition state of Prdx6, there are a lot of questions unanswered regarding the Prdx6 peroxidase activity. In order to evaluate the role of second shell conserved residue Glu50, present in close vicinity to peroxidatic active site, we substituted this negatively charged residue with Alanine and Lysine. To explore the effect of mutation on the biophysical parameters, the mutant proteins were compared with Wild-Type by using biochemical, biophysical, and in silico methods. Comparative spectroscopic methods and enzyme activity demonstrate that the Glu50 plays a significant role in maintaining the structure, stability, and function of protein. From the results we conclude that Glu50 significantly controls the structure; stability and may be involved in the active site stabilization of transition state for proper position of diverse peroxides.