The role of formate in combatting oxidative stress
The interaction of keto-acids with reactive oxygen species (ROS) is known to produce the corresponding carboxylic acid with the concomitant formation of CO2. Formate is liberated when the keto-acid glyoxylate neutralizes ROS. Here we report on how formate is involved in combating oxidative stress in the nutritionally-versatile Pseudomonas fluorescens. When the microbe was subjected to hydrogen peroxide (H2O2), the levels of formate were 8 and two-fold higher in the spent fluid and the soluble cell-free extracts obtained in the stressed cultures compared to the controls respectively. Formate was subsequently utilized as a reducing force to generate NADPH and succinate. The former is mediated by formate dehydrogenase (FDH-NADP), whose activity was enhanced in the stressed cells. Fumarate reductase that catalyzes the conversion of fumarate into succinate was also markedly increased in the stressed cells. These enzymes were modulated by H2O2. While the stressed whole cells produced copious amounts of formate in the presence of glycine, the cell-free extracts synthesized ATP and succinate from formate. Although the exact role of formate in anti-oxidative defence has to await further investigation, the data in this report suggest that this carboxylic acid may be a potent reductive force against oxidative stress.
KeywordsFormate metabolism Pseudomonas fluorescens Ketoacids Glyoxylate Formate dehydrogenase Fumarate reductase- formate dependent Isocitrate lyase
This work was supported by Laurentian University and Northern Ontario Heritage Fund Corporation. Sean C. Thomas is a recipient of the Natural Sciences and Engineering Research Council Post Graduate Scholarship-Masters. Azhar Alhasawi is a recipient of a doctoral scholarship from the Ministry of Higher Education of Saudi Arabia.
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Conflict of Interest
The authors declare that they have no conflict of interest.
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