Tyrosine is involved in protection from oxidative stress inSaccharomyces cerevisiae

Abstract

The phenotypic characterization of a Saccharomyces cerevisiae mutant unable to grow under agitated conditions is presented here. When this strain was incubated under aerobic conditions, it did not grow and the viability of the culture decreased. The loss in viability was prevented by the addition of antioxidants or chelating agents to the medium, indicating that this mutant was unable to withstand the oxidative stress generated by aerobic metabolism. This strain was complemented with plasmids from a yeast genomic library. The transformants that were obtained carried plasmids harbouring the TYR1 gene, which codes for one of the enzymes involved in tyrosine biosynthesis. A monogenic S. cerevisiae tyr1 mutant obtained from the Yeast Genetic Stock Center showed higher sensitivity to hydrogen peroxide than a TYR1 strain. This sensitivity was reverted when this strain was complemented with the TYR1 gene. Considering these results, we propose that tyrosine plays a role in the protection against oxidative stress.Key words: oxidative stress, amino acid biosynthesis, reactive oxygen intermediates, nitrogen metabolism.