gamma-Glutamyl transpeptidase (GGT, EC 2.3.2.2.) catalyzes the transfer of the gamma-glutamyl moiety from gamma-glutamylcontaining compounds, notably
glutathione (GSH), to acceptor
amino acids and
peptides. A second gene (GGTII) encoding GGT was previously isolated and characterized from the fission yeast Schizosaccharomyces pombe. In the present work, the GGTII-lacZ fusion gene was constructed and used to study the transcriptional regulation of the S. pombe GGTII gene. The synthesis of
beta-galactosidase from the GGTII-lacZ fusion gene was significantly enhanced by NO-generating SNP and
hydrogen peroxide in the wildtype yeast cells. The GGTII
mRNA level was increased in the wild-type S. pombe cells treated with SNP. However, the induction by SNP was abolished in the Pap1-negative S. pombe cells, implying that the induction by SNP of GGTII is mediated by Pap1. Fermentable
carbon sources, such as
glucose (at low concentrations),
lactose and
sucrose, as a sole
carbon source, enhanced the synthesis of
beta-galactosidase from the GGTII-lacZ fusion gene in wildtype KP1 cells but not in Pap1-negative cells.
Glycerol, a non-fermentable
carbon source, was also able to induce the synthesis of
beta-galactosidase from the fusion gene, but other non-fermentable
carbon sources such as
acetate and
ethanol were not. Transcriptional induction of the GGTII gene by fermentable
carbon sources was also confirmed by increased GGTII
mRNA levels in the yeast cells grown with them.
Nitrogen starvation was also able to induce the synthesis of
beta-galactosidase from the GGTII-lacZ fusiongene in a Pap1-dependent manner. On the basis of the results, it is concluded that the S. pombe GGTII gene is regulated by oxidative and metabolic stress.