Effect of the Radioprotector 2-Mercaptopropionylglycine (MPG) on the Radiation Inactivation of Catalase In Vitro

Abstract

Studies were performed to provide mechanistic insights into the action of the radioprotector drug, 2-mercaptopropionylglycine (MPG) following the radiolysis of catalase, a detoxifying enzyme. The enzyme solution was γ-irradiated in the presence and absence of MPG. The enzyme activity was monitored in vitro using H₂O₂ as a substrate. MPG behaved primarily as a radioprotective drug. However, due to the presence of Fe⁺⁺/Fe⁺⁺⁺, and the in homogeneity of catalase, under certain conditions there was circumstancial interaction of Fe⁺⁺/Fe⁺⁺⁺ with MPG, resulting in the formation of an unstable catalase Fe⁺⁺/Fe⁺⁺⁺-MPG chelate/complex. This resulted in the radiosensitizing effect of MPG on enzyme catalase.