Modulation of TCA cycle enzymes and aluminum stress in Pseudomonas fluorescens.
Oxalic acid plays a pivotal role in the adaptation of the soil microbe Pseudomonas fluorescens to aluminum (Al) stress. Its production via the oxidation of glyoxylate necessitates a major reconfiguration of the enzymatic reactions involved in the tricarboxylic acid (TCA) cycle. The demand for glyoxylate, the precursor of oxalic acid appears to enhance the activity of isocitrate lyase (ICL). The activity of ICL, an enzyme that participates in the cleavage of isocitrate to glyoxylate and succinate incurred a 4-fold increase in the Al-stressed cells. However, the activity of isocitrate dehydrogenase, a competitor for the substrate isocitrate, appeared to be diminished in cells exposed to Al compared to the control cells. While the demand for oxalate in Al-stressed cells also negatively influenced the activity of the enzyme alpha-ketoglutarate dehydrogenase complex, no apparent change in the activity of malate synthase was recorded. Thus, it appears that the TCA cycle is tailored in order to generate the necessary precursor for oxalate synthesis as a consequence of Al-stress.
Hamel
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Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry (GWC)2, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Appanna
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D000535:Aluminum / Q000378:metabolism / Q000494:pharmacology*; D017607:Aluminum Compounds / Q000378:metabolism / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002701:Chloramphenicol / Q000494:pharmacology; D002952:Citric Acid Cycle / Q000187:drug effects*; D006038:Glyoxylates / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007522:Isocitrate Lyase / Q000378:metabolism; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008292:Malate Synthase / Q000378:metabolism; D019815:Oxalic Acid / Q000378:metabolism; D011551:Pseudomonas fluorescens / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology; D019802:Succinic Acid / Q000378:metabolism
D017607:Aluminum Compounds; D006038:Glyoxylates; D002701:Chloramphenicol; D019815:Oxalic Acid; D019802:Succinic Acid; D000535:Aluminum; D007521:Isocitrate Dehydrogenase; D007655:Ketoglutarate Dehydrogenase Complex; D008292:Malate Synthase; D007522:Isocitrate Lyase; C031150:glyoxylic acid; D012293:Rifampin