Journal
FREE RADICAL BIOLOGY AND MEDICINE
Volume 44, Issue 3, Pages 394-402Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.freeradbiomed.2007.09.019
Keywords
oxidative stress; filamentous fungi; adaptive responses; H2O2; antioxidant enzymes
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In the present study, we used a recombinant filamentous fungus strain, Aspergillus niger B1-D, as a model system, and investigated the antioxidant defences in this organism. Our findings indicate that pretreatment with low concentrations of H2O2 completely prevents killing by this oxidant at high concentrations. It shows that A. niger adapts to exposure to H,02 by reducing growth and inducing a number of antioxidant enzyme activities, including superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, of which the induction of catalase is the most pronounced. Moreover the decline of these antioxidant enzymes activities after H2O2 detoxification, coincides with recommencement of growth. Results from monitoring the extracellular H2O2 concentration clearly indicate a very rapid detoxification rate for H2O2 in adapted A. niger cultures. A mathematical model predicts only very low concentrations of intracellular H2O2 accumulating in such cultures. Our results also show that glutathione plays a role in the oxidative defence against H2O2 in A. niger. On addition of H2O2, the intracellular pool of glutathione increases while the redox state of glutathione becomes more oxidized. (c) 2007 Published by Elsevier Inc.
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