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Measuring Nitrite and Nitrate, Metabolites in the Nitric Oxide Pathway, in Biological Materials using the Chemiluminescence Method
Published on: December 25, 2016
Nitrate reductase from Rhodopseudomonas sphaeroides
Journal of Bacteriology
|June 1, 1982
Summary
Rhodopseudomonas sphaeroides reduces nitrate to nitrite using a chromatophore-bound enzyme, but cannot assimilate or dissimilate nitrate. This nitrate reductase activity is independent of ammonia repression and declines in stationary phase.
Area of Science:
- Microbiology
- Phototrophic Bacteria Research
- Enzyme Kinetics
Background:
- Rhodopseudomonas sphaeroides is a facultative phototroph.
- Nitrate metabolism in phototrophic bacteria is not fully understood.
- The organism's ability to reduce nitrate was previously uncharacterized.
Purpose of the Study:
- To investigate the nitrate reduction pathway in Rhodopseudomonas sphaeroides.
- To characterize the enzyme responsible for nitrate reduction.
- To explore the regulation and potential significance of this enzyme.
Main Methods:
- Enzymatic assays using isolated chromatophores.
- Solubilization and kinetic analysis of the nitrate reductase.
- Studies with enzyme inhibitors and metal antagonists.
Main Results:
- Rhodopseudomonas sphaeroides reduces nitrate to nitrite but cannot assimilate or dissimilate it.
- A chromatophore-bound nitrate reductase was identified, solubilized, and characterized.
- Enzyme activity is independent of ammonia repression and declines in stationary phase.
- Molybdenum and iron are implicated in the enzymatic reduction.
Conclusions:
- The identified nitrate reductase plays a role in nitrate transformation, not assimilation, in Rhodopseudomonas sphaeroides.
- The enzyme's characteristics suggest a nonadaptive role and specific regulatory mechanisms.
- Further research is needed to elucidate the precise physiological significance of this enzyme in phototrophic bacteria.
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