Organic Acid Metabolism by Isolated <i>Rhizobium japonicum</i> Bacteroids

Stovall, Iris; Cole, Michael

doi:10.1104/pp.61.5.787

Cited by 59 publications

(47 citation statements)

References 11 publications

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“…Assays with gel-filtered (desalted) protein from nodule cytosol indicated glutamate decarboxylase activity of 4 to 5 nmol min-l (mg protein)-' at pH 6.0, showing that a valid enzyme assay was used. Our failure to detect glutamate decarboxylase in bacteroids confirms and extends the previous observation of Stovall & Cole (1978).…”

Section: Resultssupporting

confidence: 80%

Factors contributing to the accumulation of glutamate in Bradyrhizobium japonicum bacteroids under microaerobic conditions

Salminen

Streeter

1990

Journal of General Microbiology

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Previous studies with labelled N and C have indicated synthesis and accumulation of glutamate in Brudyrhizobium japonicum bacteroids under microaerobic conditions similar to those found in soybean nodules. Low 2-oxoglutarate dehydrogenase (OGDH) activity might have accounted for this observation, but similar levels of enzyme activity were found in bacteroids isolated anaerobically or aerobically and in cultured bacteria. However, OGDH from B.japonicum bacteroids was strongly inhibited by NADH, and the degree of inhibition depended on the NADH: NAD ratio. Determination of endogenous levels of NAD and NADH gave NADH: NAD ratios of 0.19 and 0.83 in bacteroids isolated under aerobic and anaerobic conditions, respectively. A ratio of 0.83 resulted in more than 50% inhibition of OGDH in uitro, and this would be consistent with channelling of 2-oxoglutarate to glutamate. [ 14C)Glutamate supplied to bacteroids was metabolized to CO, slowly relative to the respiration of malate, and essentially no labelling of products of glutamate metabolism such as arginine, proline, glutamine and 4aminobutyrate (GAB) was found. Attempts to trap 14C in GAB by supplying unlabelled GAB or transaminase inhibitors with [ 14C]glutamate were unsuccessful. The finding that glutamate decarboxylase was essentially absent in six different strains of B. japonicum was consistent with the labelling results and indicated that conversion of glutamate to succinate via GAB is slow or nil. The inhibition of OGDH by a high NADH:NAD ratio and the absence of the GAB shunt are complementary mechanisms which probably account for the accumulation of glut ama te .

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Section: Resultssupporting

confidence: 80%

Factors contributing to the accumulation of glutamate in Bradyrhizobium japonicum bacteroids under microaerobic conditions

Salminen

Streeter

1990

Journal of General Microbiology

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Section: Abstracrmentioning

confidence: 99%

“…In bacteroids, although the pathway from glucose to organic acids remains in doubt, considerable evidence exists for functional citric acid and poly-jl-hydroxybutyrate cycles (2, 8, 9, 15, 17, 21,25,28,29).…”

mentioning

confidence: 99%

“…Duing the period of developing nitrogenase activity, the specfic activity of fumuase, hydroxybutyrate dehydrogenase, ,-ketothiohlse, and pyruvate dehydrogenase complex incesed whereas acetoacetate-succinyl-CoA transferase and isocitrate dehydrogenase decreased (2,8,9,15,17,21,25,28,29).The carbon metabolism of developing and senescing nodules and the metabolism of bacteroids have been reviewed recently (5,19,27 PHB has been measured in many rhizobia species (7,12,14 The purpose of this investigation was, first, to establish that PDC, selected enzymes from the citric acid cycle, (IDH, MDH, and FMR) and of the PHB cycle (KT, HBD, and AST) were present during the period of nitrogen fixation and PHB accumulation in R. japonicum; second, to follow their activity as a function ofage; and third, to relate temporal changes in activities to those of nitrogenase and PHB accumulation through the use of dispersion diagrams. …”

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confidence: 99%

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Enzymes of the Poly-β-Hydroxybutyrate and Citric Acid Cycles of Rhizobium japonicum Bacteroids

Karr

Waters²,

Suzuki³

et al. 1984

Plant Physiol.

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ABSTRACrThe activities of several enzymes of the citric acid and poly-4e-hydroxybutyrate cycles were measured in Rhizobiumjapeoicwm 3IIB-143 bacteroids which had been isolated from soybean nodules by sucrose gradient centrifupaton. Duing the period of developing nitrogenase activity, the specfic activity of fumuase, hydroxybutyrate dehydrogenase, ,-ketothiohlse, and pyruvate dehydrogenase complex incesed whereas acetoacetate-succinyl-CoA transferase and isocitrate dehydrogenase decreased (2,8,9,15,17,21,25,28,29).The carbon metabolism of developing and senescing nodules and the metabolism of bacteroids have been reviewed recently (5,19,27 PHB has been measured in many rhizobia species (7,12,14 The purpose of this investigation was, first, to establish that PDC, selected enzymes from the citric acid cycle, (IDH, MDH, and FMR) and of the PHB cycle (KT, HBD, and AST) were present during the period of nitrogen fixation and PHB accumulation in R. japonicum; second, to follow their activity as a function ofage; and third, to relate temporal changes in activities to those of nitrogenase and PHB accumulation through the use of dispersion diagrams.

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“…Nitrogen fixation could be detected only with C4 dicarboxylic acids, not with the hexoses and disaccharides [3, 4, 121. Bacteroids possess a transport system for C4 dicarboxylic acids [ 1 1, 13 -161 and a functional tricarboxylic acid cycle [12]. The predominant C4 dicarboxylic acid in root nodules of legumes is malate [17 -201, which is synthesized from oxaloacetate and NADH by malate dehydrogenase.…”

mentioning

confidence: 99%

Identification of cytoplasmic nodule‐associated forms of malate dehydrogenase involved in the symbiosis between Rhizobium leguminosarum and Pisum sativum

Appels¹,

Haaker²

1988

European Journal of Biochemistry

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The malate dehydrogenase activity (EC 1.1.1.37), present in the cytoplasm of Pisum sativum root nodules, can be separated by ion-exchange chromatography into four different fractions. Malate dehydrogenase activity present in the cytoplasm of roots elutes mainly as a single peak.During nodule development an increase in malate dehydrogenase activity per gram of material was observed. This increase occurred concomitantly with the increase in nitrogenase activity.The kinetic properties of the separated malate dehydrogenases of root nodule cytoplasm and root cytoplasm were studied. The K , values for malate (2.6 mM), NAD' (27 pM), oxaloacetate (18 pM) and NADH (13 pM) of the dominant form of the root nodule cytoplasm are much lower than those of the dominant malate dehydrogenase root form (64 mM, 4.4 mM, 89 pM and 70 pM respectively). Binding of malate by the enzyme-NADH complex from noot nodules results in an abortive complex, thereby blocking the further reduction of oxaloacetate by NADH. The dominant root malate dehydrogenase does not form the abortive complex.From the kinetic data it is concluded, first, that the root nodule forms of the enzyme are capable of catalysing at a high rate the reduction of oxaloacetate, to meet the demands for malate governed by the bacterioid and the infected plant cell. The second conclusion, drawn from the kinetic data, is that under physiological conditions the conversion of oxaloacetate can be controlled just by the malate concentration.Consequently the major root nodule forms of malate dehydrogenase are able to allow a high flux of malate production from oxaloacetate but also to establish a sufficient oxaloacetate concentration necessary for the assimilation and transport of fixed nitrogen.In the absence of an adequate supply of available soil nitrogen, certain leguminous species are capable of forming symbiotic associations with soil bacteria of the genus Rhizobium. The intracellular symbiotic association arises in the cortex of legume roots following infection by Rhizobium. In the root cortex the bacteria cause formation of meristems. The bacteria penetrate the newly divided host cells through growth and branching of the infection threads. Released bacteria are enclosed by envelopes of host cell plasmalemma and develop into bacteroids. This differentiated form of bacteria is capable of the reduction of N2 to NH3 [I]. The continued division of infected cells and the proliferation of bacterial cells result in the formation of root nodules with a specific morphological arrangement (for a review see [2]).To allow nitrogen fixation to occur in the root nodule there must be an extensive metabolic balance between bacteroids and the different plant cells. Photosynthetic products of the host are used by the plant cells and bacteroids. Dioxygen, transported by leghemoglobin, together with carbon compounds made available to the bacteroids, are used to generate reducing power and ATP for nitrogen fixation. The product of the nitrogenase reaction, NH3, is assimilated in the cytosol of the ...

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Organic Acid Metabolism by Isolated Rhizobium japonicum Bacteroids

Cited by 59 publications

References 11 publications

Factors contributing to the accumulation of glutamate in Bradyrhizobium japonicum bacteroids under microaerobic conditions

Factors contributing to the accumulation of glutamate in Bradyrhizobium japonicum bacteroids under microaerobic conditions

Enzymes of the Poly-β-Hydroxybutyrate and Citric Acid Cycles of Rhizobium japonicum Bacteroids

Identification of cytoplasmic nodule‐associated forms of malate dehydrogenase involved in the symbiosis between Rhizobium leguminosarum and Pisum sativum

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