Schizosaccharomyces pombe homologue of glutathione peroxidase, which does not contain selenocysteine, is induced by several stresses and works as an antioxidant.

We have cloned a gene of Schizosaccharomyces pombe homologues to the glutathione peroxidase gene. The cloned gene, named gpx1(+), encoded a protein that was 158 amino acids in length and had a molecular mass of 18 kDa. The gpx1(+) gene is homologous with many glutathione peroxidase genes but the selenocysteine codon (UGA) position of mammalian genes is a cysteine codon (UGU) in S. pombe. gpx1(+) mRNA was induced by various stresses, including oxidative stress, osmostress and heat stress. These stresses activate the Wis1-Sty1/Spc1 MAP kinase cascade in S. pombe. Transcriptional factors Atf1 and Pap1 are under the control of this MAP kinase. In the disruption of the atf1(+) gene, gpx1(+) was not transcribed or induced. However, the expression of gpx1(+) was not affected by the disruption of the pap1(+) gene. These results indicated that gpx1(+) was under the control of transcription factor Atf1. Catalase can detoxicate H(2)O(2) in the same way as GPx and the disruptant of the catalase gene of S. pombe is hypersensitive to H(2)O(2). The catalase gene disruptant of S. pombe harbouring multicopy plasmid containing gpx1(+) restored the hypersensitivity to H(2)O(2) of the catalase gene disruptant. These results suggest that Gpx1 acts as a scavenger of H(2)O(2) in vivo.

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