Comunicação ao 9th ISMBM - Comparative Effects of NH4VO3 on detoxification and Redox State of Wine Saccharomyces

Abstract

Glutathione S-transferases (GST) and -glutamyl transferases (-GT) are evolutionary conserved enzymes that are important in the detoxication of many xenobiotic compounds, some oxygen reactive species (ROS) and glutathione degradation in living cells, catalyzing the conjugation of glutathione to electrophilic substrates and facilitating their removal from the cell via membrane-based glutathione conjugate pumps. Vanadium (V) is a heavy metal with ubiquitous distribution in nature, which in some cases becoming toxic because causes enzymatic inhibition and ROS formation. The aims of this work was to compare the effects of NH4VO3 on GST, -GT activities and redox state of wild wine yeast Saccharomyces cerevisiae UE-ME3 and Saccharomyces chevalieri UE-ME1. Exponential-phase cells were harvest and suspended in enriched mineral medium, containing ammonuim vanadate in a range from 0.25 to 200 mM at 28ºC during 200 minutes. Samples from each treatment were used to determine cfu and generate the respective dose-response curves. Cells growing in agar plate enriched mineral medium, in absence or presence of 25 and 75 mM NH4VO3 (S. cerevisiae) or 0.25, 0.75, 2.5 7.5 mM NH4VO3 (S. chevalieri) were harvested and disrupted with glass beads. The post-peroxissomal supernatants obtained by differential centrifugation were used for determination of GST (EC 2.5.1.18) and -GT (EC 2.3.2.2) activities and glutathione contents. Our results show that S. cerevisiae was more tolerant to NH4VO3 than S. chevalieri cells, which do not survive to concentration higher than 7.5 mM. In addition, the GST activities level and GSH/GSSG ratio determined in S. cerevisiae were higher than which were determined in S. chevalieri. Moreover the -GT enzymatic activities level determined in S. cerevisiae were lower than which were determined in S. chevalieri. We also observed that NH4VO3, a pentavalent salt of vanadium caused a decrease of GST and -GT activities in both yeast and a decrease of GSH/GSSG in S. cerevisiae, probably disturbing its detoxycation capacity and protection mechanisms against oxidative stress.