Histidine is a source of the antioxidant, α-ketoglutarate, in Pseudomonas fluorescens challenged by oxidative stress

Abstract

The role of alpha-ketoglutarate (KG) in the detoxification of reactive oxygen species (ROS) has only recently begun to be appreciated. This ketoacid neutralizes ROS in an NADPH-independent manner with the concomitant formation of succinate and CO(2). To further probe this intriguing attribute of KG in living systems, we have evaluated the significance of histidine metabolism in the model organism, Pseudomonas fluorescens, challenged by hydrogen peroxide (H(2)O(2)). Here, we show that this amino acid does contribute to KG homeostasis and appears to be earmarked for the production of KG during oxidative stress. Both the NAD- and the NADP-dependent glutamate dehydrogenases were upregulated in the stressed cells despite the sharp decline in the activities of numerous enzymes mediating the tricarboxylic acid cycle and oxidative phosphorylation. Enzymes such as isocitrate dehydrogenase-NAD dependent, succinate dehydrogenase, alpha-ketoglutarate dehydrogenase, Complex I, and Complex IV were severely affected in the P. fluorescens grown in the presence of H(2)O(2). Studies with fluorocitrate, a potent inhibitor of citrate metabolism, clearly revealed that histidine was preferentially utilized in the production of KG in the H(2)O(2)-challenged cells. Regulation experiments also helped confirm that the metabolic reprogramming, resulting in the enhanced production of KG was induced by H(2)O(2) stress. These data further establish the pivotal role that KG plays in antioxidative defense.

Metabolite profiling of sheath blight disease resistance in rice: in the case of positive ion mode analysis by CE/TOF-MS

“…Further, irreversible action of glutamate decarboxylase activity alters glutamate to GABA. Meanwhile, histidine associated with glutamate as α-ketoglutarate generator to convert histidine into glutamate (Lemire et al, 2010). Hecker et al (1975) explained that glutamate deficiency occurs in resistant variety.…”

Hierarchical nanostructures of Au@ZnO: antibacterial and antibiofilm agent

“…In our antibacterial study, since a reporter of ROS on cellular surfaces was hypothesized for the microbial destructions, the biofilm inhibition of P. aeruginosa, therefore, could occur due to a similar photocatalytic generation of ROS. Since histidine has been shown to play an important role in the oxidative stress in P. aeruginosa (Lemire et al 2010), we have Fig. 11 Effect of Ag-ZnO nanostructure on biofilm structure: Cells of P. aeruginosa (mid log phase, approx.…”

Metabolic networks to combat oxidative stress in Pseudomonas fluorescens

“…The major producers of ROS in the respiratory chain include complexes I and III (Hirst et al 2008;Murphy 2009). In addition, conditions that inhibit electron flow through the complexes can also greatly increase ROS production from the respiratory chain (Iuchi and Weiner 1996;Lemire et al 2010b). The over-supply of NADH to complex I is well-known to enhance ROS production from the respiratory chain leading to cell death (Murphy 2009).…”

“…Intriguingly, NADP-ICDH is the major NADPH-producing enzyme in ROS-exposed P. fluorescens when citrate is the sole carbon source. Cells grown in malate or histidine use ME and NADP-GDH preferentially to satisfy their NADPH demands (Lemire et al 2010b;Mailloux et al 2008). Hence, P. fluorescens utilizes a battery of NADPH-producing enzymes to combat oxidative stress.…”