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 K12 mutants lacking phenazine-methosulphate-linked formate dehydrogenase (FDH-PMS) activity, but still capable of producing normal levels of benzyl-viologen-linked formate dehydrogenase (FDH-BV) and nitrate reductase activities, have been isolated following P1 localized mutagenesis. The relevant mutations mapped with the same cotransduction frequency close to the rhaD gene, at 88 min on the E. coli chromosome. They were further subdivided into two classes. Class I consisted of six fdhD mutants which synthesized an inactive FDH-PMS protein with the same subunit composition as the wild-type enzyme. In contrast, class II contained four fdhE mutants totally devoid of this antigen. Construction of merodiploid strains harbouring various combinations of the mutated alleles, fdhE on the episome and fdhD on the chromosome, led to the restoration of FDH-PMS activity by complementation of the products encoded by the respective wild-type alleles. Difference spectroscopy suggested that both fdhD and fdhE mutants contained normal amounts of the cytochrome b559 associated with FDH-PMS although the cytochrome had lost its capacity for formate-dependent reduction.
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PMID:Mutants of Escherichia coli specifically deficient in respiratory formate dehydrogenase activity. 307 34

Nitrate reductase activity is most commonly assayed by measurement of product formation. Excess NADH and factor(s) present in the enzyme extract that interfere with the diazotization and azo color complex of nitrite cause a depression of apparent nitrate reductase activity. Two postassay treatments were found that markedly enhanced the extent of nitrite color formation and apparent nitrate reductase activity. The procedure involves stopping the reaction with zinc acetate (50 mumoles per ml of reaction mix), followed by removal of the precipitate by centrifugation. Presumably the zinc acetate removes extract factor(s) that interfere with color development, because it does not remove the NADH. Phenazine methosulfate (15 nmoles per ml of reaction mix) is added to aliquots of the supernatant and allowed to stand for 20 min at 30 C to oxidize the residual NADH before color development.
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PMID:Improvements of the nitrite color development in assays of nitrate reductase by phenazine methosulfate and zinc acetate. 1665 98