title: Control of carbon flux to glutamate excretion in Klebsiella pneumoniae: the role of the indigenous plasmid and its encoded isocitrate dehydrogenase.
abstract: Klebsiella pneumoniae (NCTC, CL687/80) harbors a large indigenous plasmid (p(C3)), which in addition to encoding for citrate utilization, proline synthesis and glutamate excretion, it uniquely carries the structural gene (icd); encoding isocitrate dehydrogenase (ICDH). Flux analysis revealed that ICDH, despite its role in the generation of NADPH required for glutamate dehydrogenase, is not rate-limiting (controlling) in central metabolism as evidenced by a negative flux control coefficient and an adverse effect of overexpression (14-fold) on glutamate excretion. More significantly, however, this paper presents, for the first time, clear evidence that the accumulation of glutamate and its subsequent excretion is associated with the C3 plasmid-encoded regulatory elements, which trigger a shift-down in the activity of α-ketoglutarate dehydrogenase, both in the K. pneumoniae parental strain as well as in the E. coli exconjugants strains. This finding opens the door for the exploitation of regulatory elements as a tool for manipulating flux in microbial cell factories.
authors.affiliation: Centre for Research and Innovation, Faculty of Science, Elizade University, Ilara Mokin, Akure, Nigeria. mel.mansi@elizadeuniversity.edu.ng.
authors.forename: Mansi
authors.initials: M
authors.lastname: El-Mansi
authors.affiliation: Department of Biology, Davidson College, Davidson, NC, USA.
authors.forename: Francois
authors.initials: F
authors.lastname: Trappey
authors.affiliation: Institute of Cell Biology, University of Edinburgh, Darwin Building, Mayfield Rd, Edinburgh, EH9 3JR, Scotland, UK.
authors.forename: Ewan
authors.initials: E
authors.lastname: Clark
authors.affiliation: Department of Biology, Davidson College, Davidson, NC, USA.|Genome Consortium for Active Teaching, Davidson, NC, USA.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Campbell
mesh_terms: D019149:Bioreactors; D057486:Carbon Cycle / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism*; D007521:Isocitrate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010957:Plasmids / Q000235:genetics* / Q000378:metabolism
chemical_list: D018698:Glutamic Acid; D009249:NADP; D007521:Isocitrate Dehydrogenase; D007655:Ketoglutarate Dehydrogenase Complex
keywords: Glutamate dehydrogenase; Glutamate excretion; Isocitrate dehydrogenase; Klebsiella pneumoniae; α-Ketoglutarate dehydrogenase