title: Oxygen regulation of alternative respiration in fungus Phycomyces blakesleeanus: connection with phosphate metabolism.
abstract: Environmental changes can often result in oxygen deficiency which influences cellular energy metabolism, but such effects have been insufficiently studied in fungi. The effects of oxygen deprivation on respiration and phosphate metabolites in Phycomyces blakesleeanus were investigated by oxygen electrode and (31)P NMR spectroscopy. Mycelium was incubated in hypoxic and anoxic conditions for 1.5, 3 and 5 h and then reoxygenated. Participation of alternative oxidase (AOX) in total respiration increased gradually in both treatments and after 5 h of anoxia exceeded a value 50% higher than in control. Shortly after reintroduction of oxygen into the system AOX level decreased close to the control level. Oxygen deprivation also caused a reversible decrease of polyphosphate/inorganic phosphate ratio (PPc/Pi), which was strongly correlated with the increase of AOX participation in total respiration. Unexpectedly, ATP content remained almost constant, probably due to the ability of PolyP to sustain energy and phosphate homeostasis of the cell under stress conditions. This was further substantiated by the effects of azide, a cytochrome c oxidase inhibitor, which also decreased PPc/Pi ratio, but to a smaller extent in oxygen deprived than control and reoxygenated specimens.
authors.affiliation: Department of Life Sciences, Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia. mstanic@imsi.rs
authors.forename: Marina
authors.initials: M
authors.lastname: Stanić
authors.forename: Joanna
authors.initials: J
authors.lastname: Zakrzewska
authors.forename: Mirzeta
authors.initials: M
authors.lastname: Hadžibrahimović
authors.forename: Milan
authors.initials: M
authors.lastname: Zižić
authors.forename: Zoran
authors.initials: Z
authors.lastname: Marković
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Vučinić
authors.forename: Miroslav
authors.initials: M
authors.lastname: Zivić
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004734:Energy Metabolism; D005656:Fungal Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010800:Phycomyces / Q000201:enzymology / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D000099188:Alternative Oxidase
chemical_list: D000255:Adenosine Triphosphate; D005656:Fungal Proteins; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010100:Oxygen; D010710:Phosphates; D010940:Plant Proteins; D000099188:Alternative Oxidase
keywords: Alternative oxidase; Anoxia; Phycomyces blakesleeanus; Polyphosphates