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

Nitrate assimilation-defective mutants SP7, SP9, and SP17 of the cyanobacterium Anabaena sp. PCC 7120 were isolated by use of transposon mutagenesis and screened on medium containing chlorate. SP7 and SP17 represented nitrate reductase-defective nature, while mutant SP9 appeared to be a regulatory mutant exhibiting pleiotropic behavior. Kinetics of nitrate uptake system exhibited K(s) values of 31-38 &mgr;M for parent, SP7, and SP17 strains; however, mutant SP9 exhibited a high K(s) value of 109.5 &mgr;M. Defective nitrate reductase was apparent in mutant SP7 and SP9, while mutant SP17 exhibited partial defective nature. Methyl viologen-dependent NR activity in parent strain presented a biphasic nature with K(m) values of 0.13 and 2.47 mM, whereas a single K(m) value (2.96 mM) was observed for mutant SP17. Mutant SP9 was also defective in nitrite uptake and reduction. Mutant strains exhibited derepressed nitrogenase activity in the presence of nitrate, while glutamine synthetase activity remained unaltered.http://link.springer-ny. com/link/service/journals/00284/bibs/39n5p237.html</HEA
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PMID:Mutants of the cyanobacterium anabaena sp. PCC 7120 altered in nitrate transport and reduction 1048 30

The presence of NaCl in the nutrient solution promoted nitrate uptake in parent Anabaena sp. PCC 7120, mutants SP7 (defective in nitrate reductase activity) and SP17 (partially defective in nitrate reductase activity), but not in the mutant SP9 (defective in nitrate transport and reduction). Nitrate reductase activity of the parent and mutant SP17 increased with increasing concentration of nitrate in saline medium, while mutants SP7 and SP9 did not respond to the altered salinity. Although Na+ was not required for nitrate reductase activity, its presence in the nutrient solution enhanced nitrate reduction. Complete removal of Na+ from the nutrient solution markedly reduced nitrogenase activity in all the strains, while raising the concentration of NaCl to 50 mmol l-1 or above, was equally toxic to nitrogenase activity. External NaCl at 200 mmol l-1 brought down the nitrogenase activity to the same residual level as observed without Na+.
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PMID:Response to NaCl of nitrate assimilation and nitrogenase activity of the cyanobacterium Anabaena sp. PCC 7120 and its mutants. 1069 73