Lap4, a vacuolar aminopeptidase I, is involved in cadmium-glutathione metabolism Paula D. B. Adamis Æ Sergio C. Mannarino Æ Cristiano J. Riger Æ Giselle Duarte Æ Ana Cruz Æ Marcos D. Pereira Æ Elis C. A. Eleutherio Received: 18 February 2008 / Accepted: 4 August 2008 / Published online: 21 August 2008 Ó Springer Science+Business Media, LLC. 2008 Abstract In Saccharomyces cerevisiae, accumula- tion of cadmium-glutathione complex in cytoplasm inhibits cadmium absorption, glutathione transferase 2 is required for the formation of the complex and the vacuolar gamma-glutamyl transferase participates of the first step of glutathione degradation. Here, we proposed that Lap4, a vacuolar amino peptidase, is involved in glutathione catabolism under cadmium stress. Saccharomyces cerevisiae cells deficient in Lap4 absorbed almost 3-fold as much cadmium as the wild- type strain (wt), probably due to the lower rate of cadmium-glutathione complex synthesis in the cyto- plasm. In wt, but not in lap4 strain, the oxidized/reduced GSH ratio and the Gtt activity increased in response to cadmium, confirming that the mutant is deficient in the synthesis of the complex probably because the degra- dation of vacuolar glutathione is impaired. Thus, under cadmium stress, Lap4 and gamma-glutamyl transferase seem to work together to assure an efficient glutathione turnover stored in the vacuole. Keywords Lap4  Cadmium  Glutathione  Mutagenesis  Saccharomyces cerevisiae Introduction Cadmium (Cd) is a heavy metal; roughly 13,000 tons are produced worldwide each year for nickel-cadmium batteries, pigments, chemical stabilizers, metal coatings and alloys. The concern arises because Cd accumulates in particular food species, with potential consequences for human health (Satarug and Moore 2004). This metal is a well known carcinogen, even at low concentrations, and a strong mutagen that acts by inhibiting DNA mismatch repair (Jin et al. 2003; Martelli et al. 2006). Last but not least, Cd causes an oxidative stress: when attacking the membranes, Cd leads to lipid peroxidation; it displaces Zn 2? and Fe 2? in proteins, resulting in their inactivation and in the iron release, which generates the highly reactive hydroxyl radical; it has a great affinity for thiols, specially glutathione (GSH), the most important antioxidant in aerobic organisms (Adamis et al. 2003; Fauchon et al. 2002; Valko et al. 2005). Oxidative stress increases ROS (reactive oxygen species) production, which has been implicated in cancer, aging, apoptosis and mutagenic effects (Jin et al. 2003; Valko et al. 2005). The mechanism of Cd detoxification is very complex and not well understood. The structural and functional similarities of genes in lower eukary- otes, like Saccharomyces cerevisiae, and mammals suggest that elucidation of the molecular mechanisms by which yeast cells protect themselves from toxic metal ions will help to direct investigations of mechanisms in human cells. P. D. B. Adamis  S. C. Mannarino  C. J. Riger  G. Duarte  A. Cruz  M. D. Pereira  E. C. A. Eleutherio (&) Departmento de Bioquı ´mica, IQ, UFRJ, 21941-909 Rio de Janeiro, RJ, Brazil e-mail: eliscael@iq.ufrj.br 123 Biometals (2009) 22:243–249 DOI 10.1007/s10534-008-9160-9