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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. A new procedure is described for selecting nitrogenase-derepressed mutants based on the method of Brenchley et al. (Brenchley, J.E., Prival, M.J. and Magasanik, B. (1973) J. Biol. Chem. 248, 6122-6128) for isolating histidase-constitutive mutants of a non-N2-fixing bacterium. 2. Nitrogenase levels of the new mutants in the presence of NH4+ were as high as 100% of the nitrogenase activity detected in the absence of NH4+. 3. Biochemical characterization of these nitrogen fixation (nif) derepressed mutants reveals that they fall into three classes. Three mutants (strains SK-24, 28 and 29), requiring glutamate for growth, synthesize nitrogenase and glutamine synthetase constitutively (in the presence of NH4+). A second class of mutants (strains SK-27 and 37) requiring glutamine for growth produces derepressed levels of nitrogenase activity and synthesized catalytically inactive glutamine synthetase protein, as determined immunologically. A third class of glutamine-requiring, nitrogenase-derepressed mutants (strain SK-25 and 26) synthesizes neither a catalytically active glutamine synthetase enzyme nor an immunologically cross-reactive glutamine synthetase protein. 4. F-prime complementation analysis reveals that the mutant strains SK-25, 26, 27, 37 map in a segment of the Klebsiella chromosome corresponding to the region coding for glutamine synthetase. Since the mutant strains SK-27 and SK-37 produce inactive glutamine synthetase protein, it is concluded that these mutations map within the glutamine synthetase structural gene.
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PMID:Regulation of nitrogen fixation. Nitrogenase-derepressed mutants of Klebsiella pneumoniae. 0 59

An L-asparaginase has been purified some 250-fold from extracts of Klebsiella aerogenes to near homogeneity. The enzyme has a molecular weight of 141,000 as measured by gel filtration and appears to consist of four subunits of molecular weight 37,000. The enzyme has high affinity for L-asparagine, with a Km below 10(-5) M, and hydrolyzes glutamine at a 20-fold lower rate, with a Km of 10(-3) M. Interestingly, the enzyme exhibits marked gamma-glutamyltransferase activity but comparatively little beta-aspartyl-transferase activity. A mutant strain lacking this asparaginase has been isolated and grows at 1/2 to 1/3 the rate of the parent strain when asparagine is provided in the medium as the sole source of nitrogen. This strain grows as well as the wild type when the medium is supplemented with histidine or ammonia. Glutamine synthetase activates the formation of L-asparaginase. Mutants lacking glutamine synthetase fail to produce the asparaginase, and mutants with a high constitutive level of glutamine synthetase also contain the asparaginase at a high level. Thus, the formation of asparaginase is regulated in parallel with that of other enzymes capable of supplying the cell with ammonia or glutamate, such as histidase and proline oxidase. Formation of the asparaginase does not require induction by asparaginase and is not subject to catabolite repression.
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PMID:L-Asparaginase of Klebsiella aerogenes. Activation of its synthesis by glutamine synthetase. 0 59

Regulation of the expression of the histidase coded by hutk of Klebsiella aerogenes in Salmonella typhimurium and in Escherichia coli and of the expression of the histidase coded by huts of S. typhimurium in E. coli was investigated. The hutk histidase was found to be sensitive to catabolite repression in K. aerogenes and in E. coli, but insensitive to catabolite repression in S. typhimurium; huts histidase has previously been shown to be catabolite sensitive in all three organisms. The expression of both hutk and huts histidase in E. coli was activated by nitrogen starvation. Apparently, the glutamine synthetase of E. coli may activate the formation of some glutamate- and ammonia-producing enzymes.
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PMID:Regulation of histidase synthesis in intergeneric hybrids of enteric bacteria. 0 26

We studied the physiology of cells of Klebsiella aerogenes containing the structural gene for glutamine synthetase (glnA) of Escherichia coli on an episome. The E. coli glutamine synthetase functioned in cells of K. aerogenes in a manner similar to that of the K. aerogenes enzyme: it allowed the level of histidase to increase and that of glutamate dehydrogenase to decrease during nitrogen-limited growth. The phenotype of mutations in the glnA site was restored to normal by the introduction of the episomal glnA+ gene. These results are consistent with the hypothesis that glutamine synthetase regulates the function of its own structural gene.
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PMID:Regulation of enzyme formation in Klebsiella aerogenes by episomal glutamine synthetase of Escherichia coli. 0 31

In Pseudomonas aeruginosa, the synthesis of histidase, urocanase and amidase is severly repressed when succinate is added to a culture growing in pyruvate + ammonium salts medium. When growth is nitrogen-limited, catabolite repression by succinate of histidase and urocanase synthesis does not occur but succinate repression of amidase synthesis persists. Amidase synthesis is not regulated in the same way as histidase synthesis by the availability of other nitrogen compounds for growth. Growth of P. aeruginosa strain PACI in succinate + histidine media is nitrogen-limited since this strain is defective in a histidine transport system. When methyl-ammonium chloride is added to succinate + histidine media, growth inhibition occurs. Mutants isolated from succinate + histidine + methylammonium chloride plates were found to be resistant to catabolite repression by succinate even in ammonium salts media. It is suggested that the hut genes of P. aeruginosa may be regulated in the same way as in Klebsiella aerogenes, by induction by urocanate and activation by either the cyclic AMP-dependent activator protein or by glutamine synthetase.
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PMID:The effect of nitrogen limitation on catabolite repression of amidase, histidase and urocanase in Pseudomonas aeruginosa. 0 23

Nitrogenase biosynthesis in Klebsiella pneumoniae including mutant strains, which produce nitrogenase in the presence of NH+4 (Shanmugam, K.T., Chan, Irene, and Morandi, C. (1975) Biochim. Biophys. Acta 408, 101--111) is repressed by a mixture of L-amino acids. Biochemical analysis shows that glutamine synthetase activity in strains SK-24, SK-28, and SK-29 is also repressed by amino acids, with no detectable effect on glutamate dehydrogenase. Among the various amino acids, L-glutamine in combination with L-aspartate was found to repress nitrogenase biosynthesis completely. In the presence of high concentrations of glutamine (1 mg/ml) even NH+4 repressed nitrogenase biosynthesis in the strains SK-27, SK-37, SK-55 and SK-56. Under these conditions, increased glutamate dehydrogenase activity was also detected. Physiological studies show that nitrogenase derepressed strains are unable to utilize NH+4 as sole source of nitrogen for biosynthesis of glutamate for biosynthesis of glutamate, whereas back mutations leading to NH+4 utilization results in sensitivity to repression by NH+4. These findings suggest that amino acids play an important role as regulators of nitrogen fixation.
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PMID:Amino acids as repressors of nitrogenase biosynthesis in Klebsiella pneumoniae. 0 1

The primary steps of N2, ammonia and nitrate metabolism in Klebsiella pneumoniae grown in a continuous culture are regulated by the kind and supply of the nitrogenous compound. Cultures growing on N2 as the only nitrogen source have high activities of nitrogenase, unadenylated glutamine synthetase and glutamate synthase and low levels of glutamate dehydrogenase. If small amounts of ammonium salts are added continuously, initially only part of it is absorbed by the organisms. After 2-3 h complete absorption of ammonia against an ammonium gradient coinciding with an increased growth rate of the bacteria is observed. The change in the extracellular ammonium level is paralleled by the intracellular glutamine concentration which in turn regulates the glutamine synthesis and an induction of glutamate dehydrogenase synthesis. Upon deadenylation these events are reversed.--Addition of dinitrophenol causes transient leakage of intracellular ammonium into the medium.
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PMID:Ammonium uptake and metabolism by mitrogen fixing bacteria. II. Klebsiella pneumoniae. 1 59

Synthesis of glutamine synthetase (GS) in anaerobic batch cultures of Escherichia coli was repressed when excess NH4+ was available, but derepressed during growth with a poor nitrogen source. In wild-type bacteria there was only a weak inverse correlation between the activities of GS and glutamate dehydrogenase (GDH) during growth in various media. No positive correlations were found between the activities of GS and nitrite reductase, or between GS and cytochrome c552: both of these proteins were synthesized normally by mutants that contained no active GS. Although activities of GS and GDH were low in two mutants that are unable to synthesize cytochrome c552 or reduce nitrite because of defects in the nirA gene, the nirA defect was separated from the GS and GDH defects by transduction with bacteriophage P1. Attempts to show that catabolite repression of proline oxidase synthesis could be relieved during NH4+ starvation also failed. It is, therefore, unlikely that nitrite reduction or proline oxidation by E. coli are under positive control by GS protein. The regulation of the synthesis of enzymes for the utilization of secondary nitrogen sources in E. coli, therefore, different from that in Klebsiella aerogenes, but is similar to that in Salmonella typhimurium.
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PMID:Lack of a regulatory function for glutamine synthetase protein in the synthesis of glutamate dehydrogenase and nitrite reductase in Escherichia coli K12. 1 79

In Klebsiella aerogenes but not in Salmonella typhimurium glutamine synthetase can function during nitrogen-limited growth to increase the rate of synthesis of histidase from the hut genes of S. typhimurium 15-59 (hutS. 15-59). Formation of proline oxidase is also not increased in nitrogen-limited cultures of S. typhimurium. However, in hybrid strains of Escherichia coli or K. aerogenes, the glutamine synthetase of S. typhimurium activates synthesis of histidase from the hutS. 15-59 genes. Apparently, glutamine synthetase is necessary but not sufficient for activation of transcription of the hut genes; another factor must also be present. This factor is active in both K. aerogenes and E. coli but is missing or altered in S. typhimurium.
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PMID:Regulation of enzyme synthesis by the glutamine synthetase of Salmonella typhimurium: a factor in addition to glutamine synthetase is required for activation of enzyme formation. 1 68

Urease was purified 24-fold from extracts of Klebsiella aerogenes. The enzyme has a molecular weight of 230,000 as determined by gel filtration, is highly substrate specific, and has a Km for urea of 0.7 mM. A mutant strain lacking urease was isolated; it failed to grow with urea as the sole source of nitrogen but did grow on media containing other nitrogen sources such as ammonia, histidine, or arginine. Urease was present at a high level when the cells were starved for nitrogen; its synthesis was repressed when the external ammonia concentration was high. Formation of urease did not require induction by urea and was not subject to catabolite repression. Its synthesis was controlled by glutamine synthetase. Mutants lacking glutamine synthetase failed to produce urease, and mutants forming glutamine synthetase at a high constitutive level also formed urease constitutively. Thus, the formation of urease is regulated like that of other enzymes of K. aerogenes capable of supplying the cell with ammonia or glutamate.
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PMID:Urease of Klebsiella aerogenes: control of its synthesis by glutamine synthetase. 1 38


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