Protection
against oxidation during dehydration of yeast.
Elenilda Pereira (1), Anita Panek (1), Elis Eleutherio (2)
(1) Biochemistry - Inst. Chemistry, UFRJ, Brig. Trompowysk s/n, Rio de Janeiro
RJ, 21949-900, Brazil; (2) Department of Biochemistry, Institut of Chemistry,
UFRJ, 21949-900, Rio de Janeiro, Brazil (eliscael@iq.ufrj.br)
Based on the
well documented notion that oxygen affects the stability of dried cells, the
role of the cytosolic and mitochondrial forms of superoxide dismutase in the
capacity of cells to resist dehydration was examined. Both enzymes are
important to improve survival and the absence of only one isoform did not
impair tolerance against dehydration. Additionally, sod strains showed the same
Sod activity than the control strain, indicating that the deficiency in either
Sod1 or Sod2 was overcome by an increase in activity of the remaining Sod. In
order to measure the level of intracellular oxidation produced by dehydration,
a fluorescent probe, 2',7'-dichlorofluorescein, was used. Dry cells exhibited a
high increase in fluorescence: both control and sod mutant strains became
almost 10-fold more oxidized after dehydration. Since one of the targets of
dehydration seems to be the membrane, we measured the level of lipid
peroxidation in cells submitted to water stress. There are several ways to
detect lipid peroxidation processes; we used the method of TBARS
(thiobarbituric acid reactive species), which detects malondialdehyde (MDA).
Dehydration produced a high increase in the levels of lipid peroxidation in
both control strain and sod mutants. Furthermore, the disaccharide
trehalose was shown to protect dry cells against oxidation.