Structure, gene expression, and evolution of primate glutathione peroxidases

Glutathione peroxidases (GPxs) are a family of enzymes that scavenge peroxides generated in cells. We carried out molecular cloning for cDNAs of four GPx isozymes (GPx-1 through 4) in primate species. The essential residues for the function of these isozymes were well conserved. A phylogenetic tree of GPx isozymes of primates and other mammals showed that GPx-4 diverged first, followed by GPx-3, GPx-2, and GPx-1. Expression of mRNAs for GPx-2 through 4 in various tissues of Japanese monkey was analyzed by Northern blot hybridization. GPx-2 mRNA was detected at 1.7 kb, exclusively in the stomach and small intestine. GPx-3 mRNA was detected at 1.8 kb, intensively in the kidney and adrenal gland, and weakly in the cerebellum, heart, and lung. GPx-4 mRNA was detected at 1.1 kb, very intensively in the testis and weakly in lung, heart, and cerebellum. These results showed that GPx isozymes were expressed under tissue-specific regulations.