Oxygen protection of nitrogenase in Frankia sp. HFPArI3.
O2 protection of nitrogenase in a cultured Frankia isolate from Alnus rubra (HFPArI3) was studied in vivo. Evidence for a passive gas diffusion barrier in the vesicles was obtained by kinetic analysis of in vivo O2 uptake and acetylene reduction rates in response to substrate concentration. O2 of NH4+-grown cells showed an apparent KmO2 of approximately 1 microM O2. In N2-fixing cultures a second Km O2 of about 215 microM O2 was observed. Thus, respiration remained unsaturated by O2 at air-saturation levels. In vivo, the apparent Km for acetylene was more than 10-fold greater than reported in vitro values. These data were interpreted as evidence for a gas diffusion barrier in the vesicles but not vegetative filaments of Frankia sp. HFPArI3.
D000114:Acetylene / Q000378:metabolism; D005658:Fungi / Q000201:enzymology*; D009591:Nitrogenase / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*; D010101:Oxygen Consumption
D009591:Nitrogenase; D000114:Acetylene; D010100:Oxygen