Flavohemoglobin detoxifies nitric oxide in aerobic, but not anaerobic, Escherichia coli. Evidence for a novel inducible anaerobic nitric oxide-scavenging activity.
Nitric-oxide dioxygenase (NOD) and reductase (NOR) activities of flavohemoglobin (flavoHb) have been suggested as mechanisms for NO metabolism and detoxification in a variety of microbes. Mechanisms of NO detoxification were tested in Escherichia coli using flavoHb-deficient mutants and overexpressors. flavoHb showed negligible anaerobic NOR activity and afforded no protection to the NO-sensitive aconitase or the growth of anoxic E. coli, whereas the NOD activity and the protection afforded with O(2) were substantial. A NO-inducible, O(2)-sensitive, and cyanide-resistant NOR activity efficiently metabolized NO and protected anaerobic cells from NO toxicity independent of the NOR activity of flavoHb. flavoHb possesses nitrosoglutathione and nitrite reductase activities that may account for the protection it affords against these agents. NO detoxification by flavoHb occurs most effectively via O(2)-dependent NO dioxygenation.
Gardner
Anne M
AM
Division of Critical Care Medicine, Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
Gardner
Paul R
PR
D000154:Aconitate Hydratase / Q000378:metabolism; D002455:Cell Division; D003486:Cyanides / Q000378:metabolism / Q000494:pharmacology; D004093:Dihydropteridine Reductase; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism*; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010105:Oxygenases / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D013997:Time Factors
D003486:Cyanides; D029968:Escherichia coli Proteins; D006420:Hemeproteins; D009569:Nitric Oxide; D010105:Oxygenases; C430724:flavohemoglobin denitrosylase; D004093:Dihydropteridine Reductase; C076538:hmp protein, E coli; D009247:NADH, NADPH Oxidoreductases; D000154:Aconitate Hydratase; D010100:Oxygen