POSSIBLE CONTRIBUTION OF THIOLS IN Na+/K+–ATPase AND δ- AMINOLEVULINIC ACID DEHYDRATASE TO THE ANTIOXIDANT CATALYTIC MECHANISM OF DIPHENYL DITELLURIDE

Abstract

The general antioxidant chemistry of organotellurium compounds have been largely related to their ability to mimic the native antioxidant enzyme, gluthathione peroxidase (GPx). However, the precise molecular event characterizing the antioxidant chemistry of this compound is yet to be fully clarified. In this study, the anioxidant chemistry of diphenyl ditelluride (DPDT) was tested in brain and spinal homogenate subjected to various prooxidants assault in the presence or absence of diamide and iodoacetamide. Furthermore, the possible contribution of thiols in Na+/K+–ATPase and δ-aminolevulinic acid dehydratase to the antioxidant catalytic mechanism of diphenyl ditelluride (DPDT) under in vitro experimental model was also tested. The results showed that DPDT inhibited cerebral and central nervous system lipid peroxidation in vitro in a concentration-dependent manner by preventing the formation of thiobarbituric acid reactive substances. Conversely, the presence of both iodoacetamide and diamide reduced the protective role of DPDT on TBARS formation under the same conditions. DPDT also inhibit both Na+/K+-ATPase and δ-aminolevulinic acid dehydratase in vitro in a concentration-dependent manner possibly by oxidising the essential thiols of these enzymes. Thus it is possible to partially conclude that the essential thiols of cerebral Na+/K+-ATPase as well as δ-ALAD may be used by diphenyl ditelluride to effect its glutathione peroxidase mimetic activity.