Putative 3-nitrotyrosine detoxifying genes identified in the yeast Debaryomyces hansenii : In silico search of regulatory sequences responsive to salt and nitrogen stress

Denitrase activity of Debaryomyces�hansenii reduces the oxidized compound 3‑nitrotyrosine in mice liver with colitis

“…To our knowledge this is the first report demonstrating that cell extracts from D. hansenii cultured in salt stress conditions have a potent denitrase activity that is able to degrade 3-NT in protein samples of liver from mice with acute colitis. Also, we demonstrated that the crude extracts of D. hansenii grown in 1 and 2 M NaCl has the highest denitrase activity, and this fact is in agreement with the postulate of the transcriptional response of D. hansenii to overcome the effects of the oxidative stress condition generated during salt stress (24,27).…”

“…Also, we considered that higher denitrase activity was reported in cell extracts of the yeast grown with 1 and 2 M NaCl (24), thus we included these cell growth conditions to obtain the cell extracts. We found that in the incubation assay, in which the samples of control and colitis liver were incubated with cells extract of D. hansenii grown in YPD medium, the higher value of 3-NT corresponded to the samples with colitis, because, first, the samples of colitis, as we described above, had a higher 3NT concentration, and second, the YPD growth condition is not stressful for the yeast and in consequence, there is only a basal denitrase activity (24). However, in the incubation assay in which the cell extract of D. hansenii grown in 1 M NaCl, the 3-NT concentration of samples with colitis decreased and dropped their values below that obtained in the control samples (Fig.…”

“…To date, a specific biological system has not been reported in higher eukaryotes that reverts the oxidation of the 3-NT bound to proteins. In a previous work, we demonstrated that D. hansenii can assimilate free 3-NT as a unique source of nitrogen and that in vitro the crude extracts of this yeast have denitrase activity (24), but it is necessary to provide evidence on whether or not such denitrase activity may function with 3-NT bound to proteins. To our knowledge this is the first report demonstrating that cell extracts from D. hansenii cultured in salt stress conditions have a potent denitrase activity that is able to degrade 3-NT in protein samples of liver from mice with acute colitis.…”

“…As we mentioned, recently we found that D. hansenii can assimilate 3-NT as unique nitrogen source, and determined that the cell extract of this yeast has denitrase specific activity over residual free 3-NT (24). However, it is necessary determine whether the cell extracts of D. hansenii can revert the 3-NT oxidation when it is bound to proteins of higher eukaryotic organisms.…”

“…In the yeast Debaryomyces hansenii (D. hansenii), we found genes that encode for NADPH-dependent monooxygenase enzymes, and in total protein extracts of the yeast, we measured the specific activity of the denitrase with commercial free 3-nitrotyrosine and determined that D. hansenii can degrade to a concentration of 10 mM 3-NT. It was also found that the yeast can assimilate 3-NT as the sole source of nitrogen (24).…”