title: The interactions of vanadium with Phycomyces blakesleeanus mycelium: enzymatic reduction, transport and metabolic effects.
abstract: The biological and chemical basis of vanadium action and transport in fungi is relatively poorly understood. In this study we investigated the interactions of vanadium in physiologically-relevant redox states: vanadate (+5) and vanadyl (+4), with mycelium of fungus Phycomyces blakesleeanus using EPR and (31)P NMR spectroscopy and biochemical assays. We determined that P. blakesleeanus reduces V(5+) to V(4+) in the extracellular compartment by the means of cell surface enzyme with ferricyanide reductase activity, which contains molybdenum-molybdopterin as a cofactor. Both, V(5+) and V(4+) bind to cell wall. They enter the cytoplasm via phosphate transporter and cation channels, respectively, and exhibit different metabolic effects. Vanadate provokes increased biomass production, the effects being inverted to toxic at higher V(5+) concentrations. In addition, V(5+) activates the synthesis of sugar phosphates and oligophosphates. On the other hand, V(4+) exhibits toxic effects even at low concentrations. The V(4+) detoxification route involves binding to vacuolar polyphosphates. Altogether our results imply that the mechanism of interaction of vanadium with P. blakesleeanus involves three major steps: extracellular enzymatic V(5+)/V(4+) reduction, V(4+) influx, and vacuolar storage, with an additional step - V(5+) import occurring at higher vanadate concentrations.
authors.affiliation: Department of Life Sciences, Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia. mzizic@imsi.rs
authors.forename: Milan
authors.initials: M
authors.lastname: Žižić
authors.forename: Miroslav
authors.initials: M
authors.lastname: Živić
authors.forename: Ivan
authors.initials: I
authors.lastname: Spasojević
authors.forename: Jelena
authors.initials: J
authors.lastname: Bogdanović Pristov
authors.forename: Marina
authors.initials: M
authors.lastname: Stanić
authors.forename: Tijana
authors.initials: T
authors.lastname: Cvetić-Antić
authors.forename: Joanna
authors.initials: J
authors.lastname: Zakrzewska
mesh_terms: D001692:Biological Transport; D004789:Enzyme Activation; D007700:Kinetics; D025282:Mycelium / Q000737:chemistry / Q000378:metabolism*; D010800:Phycomyces / Q000378:metabolism*; D014639:Vanadium / Q000378:metabolism*
chemical_list: D014639:Vanadium