title: Overexpression of isocitrate lyase is an important strategy in the survival of Pseudomonas fluorescens exposed to aluminum.
abstract: Isocitrate lyase, ICL (EC 4.1.3.1), an enzyme that cleaves isocitrate into succinate, and glyoxylate appears to play a pivotal role in the detoxification of aluminum (Al) in Pseudomonas fluorescens. Here, we present evidence that the 4-fold increase in ICL activity observed in Al-stressed cells is due to the overexpression of this enzyme. Blue-Native-PAGE, Western blotting, and spectrophotometric experiments revealed that ICL is optimally expressed at 35 h of growth in Al-stressed cells. However, following the immobilization of Al, at 60 h of growth, the level of the enzyme decreases markedly. This enzyme that exists as a homotetramer with a molecular mass of approximately 133 kDa appears to be transcriptionally regulated. The overexpression of ICL may be a specific response to Al-stress as P. fluorescens grown in the presence of such metals as Ga3+, Pb2+, and Ca2+ does not undergo any significant increase in ICL activity. Thus, these findings support the notion that the overexpression of ICL plays a pivotal role in the survival and in the increased oxalogenesis observed in Al-stressed P. fluorescens.
authors.affiliation: Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ont., Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Hamel
authors.forename: Vasu D
authors.initials: VD
authors.lastname: Appanna
authors.forename: Thammaiah
authors.initials: T
authors.lastname: Viswanatha
authors.forename: Simone
authors.initials: S
authors.lastname: Puiseux-Dao
mesh_terms: D000535:Aluminum / Q000378:metabolism / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression / Q000187:drug effects; D006038:Glyoxylates / Q000378:metabolism; D007522:Isocitrate Lyase / Q000096:biosynthesis* / Q000378:metabolism; D008670:Metals / Q000494:pharmacology; D019906:Nuclear Magnetic Resonance, Biomolecular; D011551:Pseudomonas fluorescens / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D006038:Glyoxylates; D008670:Metals; D019802:Succinic Acid; D000535:Aluminum; D007522:Isocitrate Lyase; C031150:glyoxylic acid