Oxidative Stress Induction by Perchloric Acid and Its Impact on Protein Threonine Phosphatases in Arachis hypogea L

Abstract

The protein threonine phosphatases (PThPases) catalyze the reversible phosphorylation of threonine residues in proteins and regulate numerous cellular processes, including developmental and signalling in eukaryotes. This study investigates the activity of PThPases in peanut (Arachis hypogea L.) seedlings under oxidative stress included by various oxidizing agents. Peanut seedlings grown in the dark at 28 ± 2^oC showed a several fold increase in PThPase activity during 6-8 days of germination. 8 days old germinated seedlings were treated with 2% solution of different oxidizing agents (H₂O₂, HNO₃, K₂Cr₂O₇, HClO₄, KMnO₄, MnO₂, PbO₂, and (NH₄)₂S₂O₈). Perchloric acid caused the most significant reduction in PThPases activity. Treatment of seedlings with 0.5-5% perchloric acid revealed that 4% HClO₄reducd the specific activity by approximately 65%. Exposure to 3% HClO₄ for 1-6 h showed maximum inhibition (88%) at 4 h. Among seedling parts treated with 4% HClO₄ for 4 h, hypocotyls exhibited the greatest reduction in activity, followed by epicotyls, cotyledons, and roots. SDS-PAGE showed disappearance or suppression of several protein bands in stressed tissues. These findings suggest that perchloric acid acts as a potent oxidative stress trigger and inhibitor of intracellular PThPases in peanut seedlings.