Transthyretin Stimulates Autooxidation of Reduced Glutathione

ABSTRACT

When reduced glutathione(GSH) was incubated at neutral pH and at 37degrees, its concentration decteased slowly with formation of oxidized glutathione(GSSG). Autooxidation of GSH was accelerated by Cu2+ and Hg2+, but not by other common mono-, di-, and tri-valent cations. Tranthyretin was found to stimulate autooxidation of GSH in the presence or absence of Cu2+ and Hg2+. EDTA inhibited perfectly the autooxidation of GSH regardless of the presence of transthyretin. The stimulating activity of transthyretin was maximal at pH 7.0, declining progressively with increase or decrease of pH from 7.0. Sulfhydryl-blocking agents such as p-hydroxymercuribenzoic acid and N-ethylmaleimide markedly inhibited the stimulating activity of transthyretin. Transthyretin stimulated autooxidation of other sulfhydryl compounds such as dithiothreitol and cysteine. However, it did not show a significant effect on autooxidation of sulfhydryl group of egg albumin and eye lens proteins. And transthyretin did not cause any oxidative change to thyroxine(T4), 3, 5, 3'-tri iodo thyronine(T3) and 3, 3', 5'-triiodothyronine(rT3) bound to it in the presence of GSH and Cu2+. The above results suggest that transthyretin may play a role in regulation of oxidized status of sulfhydryl groups in blood plasma and cerebrospinal fluid.