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.[1]References
- Oxygen protection of nitrogenase in Frankia sp. HFPArI3. Murry, M.A., Fontaine, M.S., Tjepkema, J.D. Arch. Microbiol. (1984) [Pubmed]
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