Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Escherichia coli growing anaerobically respond to NO3- plus PQ2+ with a 20-30-fold induction of an inactive form of the manganese-containing superoxide dismutase (MnSOD). Mutants lacking a functional nitrate reductase fail to show this response. This inactive enzyme can be activated by addition of Mn(II) salts to cell extracts in the presence of acidic guanidinium chloride, followed by dialysis against neutral buffer. Direct addition of Mn(II) to cell extracts does not result in activation. However, addition of Mn(II) to purified apo-MnSOD results in partial activation. Inactive, reconstitutable MnSOD is induced 13-fold within 15 min of exposure to NO3- plus PQ2+. Western blot analysis revealed a 15-fold increase in immunoreactive MnSOD under these conditions, suggestive of de novo synthesis of this protein. A strain of E. coli bearing a multicopy plasmid carrying the MnSOD gene (sodA) overproduces inactive MnSOD 19-fold compared to the parent strain under anaerobic conditions. Strains of E. coli with an inactivating insertion in the sodA gene do not induce inactive, reconstitutable MnSOD in response to NO3- plus PQ2+ and lack the immunoreactive MnSOD band. These results, in toto, suggest that the inactive protein synthesized under anaerobic conditions in the presence of NO3- plus PQ2+, acting as an electron sink, is a product of the sodA gene and is devoid of activity due to occupation of the manganese site by another metal.
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PMID:Anaerobic induction of ProMn-superoxide dismutase in Escherichia coli. 264 72

Escherichia coli growing anaerobically respond to NO3- with a 3-fold induction of the iron-containing superoxide dismutase. Mutants lacking nitrate reductase do not show this response. Anaerobically grown cells also contain an inactive form of the manganese-containing superoxide dismutase (MnSOD) which can be activated by addition of Mn(II) salts in the presence of acidic guanidinium chloride, followed by dialysis against neutral buffer. Direct addition of Mn(II) to a neutral solution of the inactive MnSOD does not impart activity. This inactive MnSOD thus behaves as would the apoenzyme or the enzyme bearing a metal other than Mn(II) at its active sites. Terminal electron acceptors, such as NO3- or trimethylamine N-oxide, increase the amount of inactive MnSOD produced by anaerobic E. coli. Paraquat, which is itself ineffective in this regard, markedly augments the effect of these terminal electron acceptors. It appears that flow of electrons to sinks such as NO3- or trimethylamine N-oxide, facilitated by paraquat, is sufficient to elicit biosynthesis of the MnSOD protein and that O2- is not needed for this process. Yet, oxygenation and concomitant O2- production do appear important for the insertion of manganese into the growing MnSOD polypeptide, possibly because O-2 oxidizes Mn(II) to Mn(III), and the latter is the valence state most effective in combining with the apoenzyme.
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PMID:Inductions of superoxide dismutases in Escherichia coli under anaerobic conditions. Accumulation of an inactive form of the manganese enzyme. 327 33