Maleylacetoacetate Isomerase (MAAI) belongs to the Glutathione S-Transferase super-family. MAAI encodes multifunctional enzymes in the detoxification of electrophilic molecules by conjugation with glutathione, for example, mutagens, carcinogens and several therapeutic drugs. MAAI is a bifunctional protein with low glutathione peroxidase activity with T-butyl and cumene hydroperoxides. MAAI can catalyze the glutathione dependent oxygenation of dichloroacetic acid to glyoxylic acid. But it has minimal glutathione-conjugating activity with 7-chloro-4-nitrobenz-2-oxa-1, ethacrynic acid 3-diazole and maleylacetoacetate isomerase activity.