title: Uptake and export of citric acid by Aspergillus niger is reciprocally regulated by manganese ions.
abstract: The uptake as well as the export of citric acid by Aspergillus niger occur by active, deltapH-driven, H(+)-symport dependent systems. They are inhibited by nonmetabolizable tricarboxylic acid analogues and phthalic acid, and by several other mono-, di- and tribasic organic acids. However, citrate export could only be demonstrated in a mycelium cultivated under manganese-deficient growth conditions, whereas the uptake of citrate from the medium was only detectable upon precultivation of A. niger in a medium supplemented with Mn2+ ions. In addition, the uptake of citrate was dependent on the presence of Mn2+ ions in the assay, and inhibited by EDTA. This requirement for Mn2+ could also be partially fulfilled by Mg2+, Fe2+ or Zn2+, whereas Cu2+ ions inhibited citrate transport. The observed divergent effects of manganese ions on citrate uptake and citrate export may be a major reason for the well documented requirement for manganese deficiency of citric acid accumulation.
authors.affiliation: Abteilung für Mikrobielle Biochemie, Institut für Biochemische Technologie und Mikrobiologie, TU Wien, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Netik
authors.forename: N V
authors.initials: NV
authors.lastname: Torres
authors.forename: J M
authors.initials: JM
authors.lastname: Riol
authors.forename: C P
authors.initials: CP
authors.lastname: Kubicek
mesh_terms: D001234:Aspergillus niger / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002264:Carboxylic Acids / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D019343:Citric Acid / Q000378:metabolism*; D003470:Culture Media; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology*; D008670:Metals / Q000494:pharmacology
chemical_list: D002264:Carboxylic Acids; D002413:Cations, Divalent; D003470:Culture Media; D008670:Metals; D019343:Citric Acid; D008345:Manganese; D004492:Edetic Acid