The role of glutathione in detoxification of chromate by Hansenula (Ogataea) polymorpha yeast
Aim. Chromate is very toxic, displays mutagenic and carcinogenic activity and its pollution poses a serious environment problem. The development of efficient methods for detoxification of this oxyanion is of great importance. For microbial cells, it is known that chromate transported in cells can be reduced to less toxic Cr3+. The most powerful chromate reductants could be glutathione (GSH) or cysteine. The role of GSH in detoxification of chromate by the yeast Hansenula polymorpha was evaluated. Methods. For this purpose recombinant strains with overexpressed GSH2 and MET4 genes and mutant defective in GSH biosynthesis were used. Profiles of GSH and chromium contents as well as rate of reduction of chromate were studied in relation to chromate resistance/sensitivity of the wild- type and mutant yeast strains. Results. High level of GSH in recombinant strains of H. polymorpha slightly changed the sensitivity/tolerance to chromate, but increased the rate of reduction of Cr6+ and reduces the amount of chromium accumulated in the cells. Deletion of GSH2 gene, encoding the enzyme of the first reaction of GSH synthesis, leads to increased sensitivity to the action of chromate. Conclusions. GSH can be considered as an important part of chromate detoxification system in H. polymorpha.
Keywords: glutathione, chromium, yeast, chromate reduction, Hansenula (Ogataea) polymorpha.
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