Glutathione reductase from Phaeodactylum tricornutum: purification and characterization.

ARIAS, DIEGO; MÁRQUEZ, VANINA; BECCARIA, ALEJANDRO J.; GUERRERO, SERGIO A.; IGLESIAS, ALBERTO A.

Mar del Plata – Buenos Aires - Argentina

Congreso; SAIB - XLIII Reunión Anual; 2007

The cellular redox state is a crucial mediator of multiple metabolic, signalling and transcriptional processes in the cells. Glutathione (GSH) is a widely distributed low molecular weight thiol, which provides reducing equivalents to the cell under conditions of oxidative stress, being oxidized to glutathione disulfide (GSSG) in the process. The enzyme glutathione reductase, a member of pyridine nucleotide-disulfide oxidereductase family, uses the reducing power of NADPH to regenerate GSH from GSSG. Diatoms, brown unicellular algae, are important components of marine phytoplankton, being particularly relevant for geochemical cycling of minerals, and global carbon fixation. As a consequence of their importance in the global ecosystem, their ecology and physiology have been the focus of research. In this work, a putative glutathione reductase was purified from cellular extracts of P. tricornutum and functional characterized. The Km value for NADPH and GSSG were 14 and 32 mM respectively. The enzyme was specific for NADPH but not for NADH as electron donor. The enzyme activity was markedly inhibited by metal ions such as Cu2+, Zn2+, Co2+ and Ni2+. The activity was maximum at pH 8.0 and 32 ºC. Our results strongly support the occurrence of the GSH system in P. tricornutum, which was poor previously described in this diatom. Granted by UNL, CAI+D 2002; ANPCyT, PICT´03 01-14733, PAV´03 137.