Purification and properties of the glutathione S-transferases from the anoxia-tolerant turtle, Trachemys scripta elegans.

Glutathione S-transferases (GSTs) play critical roles in detoxification, response to oxidative stress, regeneration of S-thiolated proteins, and catalysis of reactions in nondetoxification metabolic pathways. Liver GSTs were purified from the anoxia-tolerant turtle, Trachemys scripta elegans. Purification separated a homodimeric (subunit relative molecular mass =34 kDa) and a heterodimeric (subunit relative molecular mass = 32.6 and 36.8 kDa) form of GST. The enzymes were purified 23–69-fold and 156–174-fold for homodimeric and heterodimeric GSTs, respectively. Kinetic data gathered using a variety of substrates and inhibitors suggested that both homodimeric and heterodimeric GSTs were of the α class although they showed significant differences in substrate affinities and responses to inhibitors. For example, homodimeric GST showed activity with known α class substrates, cumene hydroperoxide and p-nitrobenzylchloride, whereas heterodimeric GST showed no activity with cumene hydroperoxide. The specific activity of liver GSTs with chlorodinitrobenzene (CDNB) as the substrate was reduced by 2.6- and 8.7-fold for homodimeric and heterodimeric GSTs isolated from liver of anoxic turtles as compared with aerobic controls, suggesting an anoxia-responsive stable modification of the protein that may alter its function during natural anaerobiosis. [ABSTRACT FROM AUTHOR]