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

2-Ketogluconic acid and, to a lesser extent, gluconic acid were found to be major products of glucose catabolism by phosphate-limited cultures of Klebsiella aerogenes NCTC 418, and together accounted for up to 46% of the glucose carbon that was metabolized. Although the concentrations of both acids increased substantially at low growth rates, their specific rates of synthesis decreased markedly, ad did the proportion of glucose converted into these products. Determination of the affinity constant, for glucose, of phosphate-limited organisms showed it ot be not significantly different from that of glucose-limited organisms (KS less than or equal to 50 muM), indicative of the phosphotransferase uptake system. And since these organisms possessed an active glucose 6-phosphate dehydrogenase, and had no detectable glucose dehydrogenase activity, it was concluded that gluconic acid and 2-keto-gluconic acid arose from their corresponding phosphorylated metabolites, and not directly from glucose.
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PMID:Production of gluconic acid and 2-ketogluconic acid by Klebsiella aerogenes NCTA 418. 110 45

Magnesium-limited chemostat cultures of Klebsiella pneumoniae NCTC 418 with 20 microM CaCl2 in the medium showed a low rate of gluconate plus 2-ketogluconate production relative to potassium- or phosphate-limited cultures. However, when the medium concentration of CaCl2 was increased to 1 mM, the glucose dehydrogenase (GDH) activities also increased and became similar to those observed in potassium- or phosphate limited cultures. It is concluded that this is due to Mg2+ and Ca2+ ions being involved in the binding of pyrroloquinoline quinone (PQQ) to the GDH apoenzyme. There seems to be an absolute requirement of divalent cations for proper enzyme functioning and in this respect Ca2+ ions could replace Mg2+ ions. The high GDH activity which has been found in cells grown under Mg2(+)-limited conditions in the presence of higher concentrations of Ca2+ ions, is compatible with the earlier proposal that GDH functions as an auxiliary energy generating system involved in the maintenance of high transmembrane ion gradients.
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PMID:The role of magnesium and calcium ions in the glucose dehydrogenase activity of Klebsiella pneumoniae NCTC 418. 216 Feb 28

No holoenzyme pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase and only very low apoenzyme levels could be detected in cells of Klebsiella pneumoniae, growing anaerobically, or carrying out a fumarate or nitrate respiration. Low glucose dehydrogenase activity in some aerobic glucose-excess cultures of K. pneumoniae (ammonia or sulphate limitation) was increased significantly by addition of PQQ, whereas in cells already possessing a high glucose dehydrogenase activity (phosphate or potassium limitation) extra PQQ had almost no effect. These observations indicate that the glucose dehydrogenase activity in K. pneumoniae is modulated by both PQQ synthesis and synthesis of the glucose dehydrogenase apo-enzyme.
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PMID:The separate roles of PQQ and apo-enzyme syntheses in the regulation of glucose dehydrogenase activity in Klebsiella pneumoniae NCTC 418. 253 92

Klebsiella pneumoniae NCTC 418 was cultured aerobically in chemostat cultures (D = 0.3 h-1; 35 degrees C) under respectively carbon-, phosphate-, potassium-, sulphate-, and ammonia-limited conditions with glucose as the sole carbon and energy source. The effect of the external pH value on glucose metabolism and on the enzymes of the direct glucose oxidative pathway was examined. The pH value of the medium had a profound influence on both the activity and the synthesis of the glucose dehydrogenase and the gluconate dehydrogenase. At pH values ranging from pH 5.5 to pH 6.0 maximal activity and synthesis of these enzymes resulted in a more than 80% conversion of the glucose consumed into gluconate and 2-ketogluconate under potassium- or phosphate-limited conditions. On the other hand, no gluconate and/or 2-ketogluconate production could be detected when K. pneumoniae was cultured at pH 8.0. Whereas the synthesis of gluconate dehydrogenase seemingly was completely repressed, still some glucose dehydrogenase was present. The lack of glucose dehydrogenase activity at pH 8.0 was shown not to be due to the dissociation of the cofactor PQQ from the enzyme.
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PMID:The influence of the culture pH value on the direct glucose oxidative pathway in Klebsiella pneumoniae NCTC 418. 265 Jun 50

Klebsiella aerogenes possesses a PQQ-linked glucose dehydrogenase. Other members of the Enterobacteriaceae, such as Escherichia coli, Salmonella typhimurium or Serratia marcescens are seemingly unable to synthesize PQQ, but are able to synthesize the glucose dehydrogenase apoenzyme. The physiological significance of this enzyme is discussed.
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PMID:PQQ-linked enzymes in enteric bacteria. 285 84

Quinoprotein glucose dehydrogenase (EC 1.1.99.17) from Acinetobacter calcoaceticus L.M.D. 79.41 was purified to homogeneity. It is a basic protein with an isoelectric point of 9.5 and an Mr of 94,000. Denaturation yields two molecules of PQQ/molecule and a protein with an Mr of 48000, indicating that the enzyme consists of two subunits, which are probably identical because even numbers of aromatic amino acids were found. The oxidized enzyme form has an absorption maximum at 350 nm, and the reduced form, obtained after the addition of glucose, at 338 nm. Since double-reciprocal plots of initial reaction rates with various concentrations of glucose or electron acceptor show parallel lines, and substrate inhibition is observed for glucose as well as for electron acceptor at high concentrations, a ping-pong kinetic behaviour with the two reactants exists. From the plots, Km values for glucose and Wurster's Blue of 22 mM and 0.78 mM respectively, and a Vmax. of 7.730 mumol of glucose oxidized/min per mg of protein were derived. The enzyme shows a broad substrate specificity for aldose sugars. Cationic electron acceptors are active in the assay, anionic acceptors are not. A pH optimum of 9.0 was found with Wurster's Blue and 6.0 with 2,6-dichlorophenol-indophenol. Two types of quinoprotein glucose dehydrogenases seem to exist: type I enzymes are acidic proteins from which PQQ can be removed by dialysis against EDTA-containing buffers (examples are found in Escherichia coli, Klebsiella aerogenes and Pseudomonas sp.); type II enzymes are basic proteins from which PQQ is not removed by dialysis against EDTA-containing buffers (examples are found in A. calcoaceticus and Gluconobacter oxydans).
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PMID:Purification and characterization of quinoprotein glucose dehydrogenase from Acinetobacter calcoaceticus L.M.D. 79.41. 380 Sep 75

In order to assess the functional significance of the quinoprotein glucose dehydrogenase recently found to be present in K+ -limited Klebsiella aerogenes, a broad study was made of the influence of specific environmental conditions on the cellular content of this enzyme. Whereas high activities were manifest in cells from glucose containing chemostat cultures that were either potassium- or phosphate-limited, only low activities were apparent in cells from similar cultures that were either glucose-, sulphate- or ammonia-limited. With these latter two cultures, a marked increase in glucose dehydrogenase activity was observed when 2,4-dinitrophenol (1 mM end concentration) was added to the growth medium. These results suggested that the synthesis of glucose dehydrogenase is not regulated by the level of glucose in the growth medium, but possibly by conditions that imposed an energetic stress upon the cells. This conclusion was further supported by a subsequent finding that K+ -limited cells that were growing on glycerol also synthesized substantial amounts of glucose dehydrogenase. The enzyme was found to be membrane associated, and preliminary evidence has been obtained that it is located on the periplasmic side of the cytoplasmic membrane and functionally linked to the respiratory chain. This structural and functional orientation is consistent with glucose dehydrogenase serving as a low impedance energy generating system.
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PMID:The functional significance of glucose dehydrogenase in Klebsiella aerogenes. 390 71

The recently determined primary structure of glucose dehydrogenase from Bacillus megaterium was scanned by computerized comparisons for similarities with known polyol and alcohol dehydrogenases. The results revealed a highly significant similarity between this glucose dehydrogenase and ribitol dehydrogenase from Klebsiella aerogenes. Sixty-one positions of the 262 in glucose dehydrogenase are identical between these two proteins (23% identity), fitting into a homology alignment for the complete polypeptide chains. The extent of similarity is equivalent to that between other highly divergent but clearly related dehydrogenases (two zinc-containing alcohol dehydrogenases, 25%; sorbitol and zinc-containing alcohol dehydrogenases, 25%; ribitol and non-zinc-containing alcohol dehydrogenases, 20%), and suggests an ancestral relationship between glucose and ribitol dehydrogenases from different bacteria . The similarities fit into a previously suggested evolutionary scheme comprising short and long alcohol and polyol dehydrogenases, and greatly extend the former group to one composed of non-zinc-containing alcohol-polyol-glucose dehydrogenases.
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PMID:Extended superfamily of short alcohol-polyol-sugar dehydrogenases: structural similarities between glucose and ribitol dehydrogenases. 642 Jan 86

In Klebsiella pneumoniae, six genes, constituting the pqqABCDEF operon, which are required for the synthesis of the cofactor pyrroloquinoline quinone (PQQ) have been identified. The role of each of these K. pneumoniae Pqq proteins was examined by expression of the cloned pqq genes in Escherichia coli, which cannot synthesize PQQ. All six pqq genes were required for PQQ biosynthesis and excretion into the medium in sufficient amounts to allow growth of E. coli on glucose via the PQQ-dependent glucose dehydrogenase. Mutants lacking the PqqB or PqqF protein synthesized small amounts of PQQ, however. PQQ synthesis was also studied in cell extracts. Extracts made from cells containing all Pqq proteins contained PQQ. Lack of each of the Pqq proteins except PqqB resulted in the absence of PQQ. Extracts lacking PqqB synthesized PQQ slowly. Complementation studies with extracts containing different Pqq proteins showed that an extract lacking PqqC synthesized an intermediate which was also detected in the culture medium of pqqC mutants. It is proposed that PqqC catalyzes the last step in PQQ biosynthesis. Studies with cells lacking PqqB suggest that the same intermediate might be accumulated in these mutants. By using pqq-lacZ protein fusions, it was shown that the expression of the putative precursor of PQQ, the small PqqA polypeptide, was much higher than that of the other Pqq proteins. Synthesis of PQQ most likely requires molecular oxygen, since PQQ was not synthesized under anaerobic conditions, although the pqq genes were expressed.
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PMID:Synthesis of pyrroloquinoline quinone in vivo and in vitro and detection of an intermediate in the biosynthetic pathway. 766 88

Periplasmic oxidation of glucose into gluconate and 2-ketogluconate in Klebsiella pneumoniae occurs via glucose dehydrogenase (GDH) and gluconate dehydrogenase (GaDH), respectively. Since, as is shown here, in the presence of glucose, gluconate and 2-ketogluconate are not further metabolized intracellularly the physiological function of this periplasmic route was studied. It was found that periplasmic oxidation of glucose could function as an alternative production route of ATP equivalents. Instantaneous activation of either GDH or GaDH reduced the rate of degradation of glucose via glycolysis and the tricarboxylic acid (TCA) cycle in vivo. Furthermore, aerobic, magnesium- and phosphate-limited chemostat cultures with glucose as the carbon source showed high GDH plus GaDH activities in contrast to nitrogen- and sulphate-limited cultures. However, when fructose, which is not degraded by GDH, was the carbon source, specific oxygen consumption rates under these four conditions were essentially the same. The latter observation suggests that high transmembrane phosphate gradients which are supposedly present under phosphate-limited conditions do not cause high energetic demands due to futile cycling of phosphate ions. In addition, dissipation of the transmembrane phosphate gradient of phosphate-limited cells immediately increased the rate of intracellular glucose degradation. It is concluded that under phosphate-limited conditions (i) extensive futile cycling of phosphate ions is absent and (ii) low concentrations of phosphate ions limit intracellular degradation of glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The physiological function of periplasmic glucose oxidation in phosphate-limited chemostat cultures of Klebsiella pneumoniae NCTC 418. 795 95


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