Localization of Enzymes of Ureide Biosynthesis in Peroxisomes and Microsomes of Nodules

Hanks, Joanna F.; Tolbert, N. E.; Schubert, Karel R.

doi:10.1104/pp.68.1.65

Cited by 136 publications

(70 citation statements)

References 21 publications

(21 reference statements)

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“…This work, however, is contradictory to previous work showing that XDH is a soluble enzyme (3,19). We interpret the peroxisomal labeling proposed by Nguyen et al (18) to be nonspecific labeling of plastids, since their labeled organelles appear to be too large to be considered peroxisomes, whereas plastids are of this size and are known to give nonspecific labeling.…”

Section: Discussioncontrasting

confidence: 55%

Localization of xanthine dehydrogenase in cowpea root nodules: implications for the interaction between cellular compartments during ureide biogenesis.

Datta

Triplett

Newcomb

1991

Proc. Natl. Acad. Sci. U.S.A.

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Immunocytochemistry was used to assess the location of xanthine dehydrogenase (EC 1.1.1.204) in the infected region of nodules of cowpea (Vigna unguiculata [L.] Walpers cv. Queen Anne Blackeye). Polyclonal antibodies raised against purified cowpea xanthine dehydrogenase were used to localize this enzyme at the electron microscopic level. Sparse nonspecific labeling was observed after treatment of nodule sections with preimmune serum. Although immune serum cross-reacted with the ground cytoplasm of both infected and uninfected cells, significantly more labeling was observed in the uninfected cells. No labeling above background was observed in peroxisomes, mitochondria, proplastids, endoplasmic reticulum, cytoplasmic or peribacteroid membranes, peribacteroid spaces, or bacteroids. The enzyme is soluble and not present in any organelle or membrane. The greater concentration of xanthine dehydrogenase in the uninfected cells suggests that xanthine or a precursor to xanthine, rather than uric acid, is the intermediate that moves from infected to uninfected cells during ureide biogenesis.

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Section: Discussioncontrasting

confidence: 55%

Localization of xanthine dehydrogenase in cowpea root nodules: implications for the interaction between cellular compartments during ureide biogenesis.

Datta

Triplett

Newcomb

1991

Proc. Natl. Acad. Sci. U.S.A.

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“…A number of reports (1,6,8,28,33,34) indicate the presence of several of the enzymes of purine catabolism in the nodule tissue of ureide-exporting plants. Xanthine dehydrogenase, uricase, and allantoinase activities were measured during plant development and are reported in Figure 5.…”

Section: Resultsmentioning

confidence: 99%

Enzymes of Purine Biosynthesis and Catabolism in Glycine max

Schubert¹

1981

Plant Physiol.

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During the period examined from 12 to 63 days after planting, the ureides, allantoin and allantoic acid, were fixation (C2H2) from day 18 reaching a maximum value of 13.9 micromoles per plant per hour at day 49, and then both activities declined rapidly. During the period of active nitrogen fixation the ratio of PRPP synthesis estimated from measurements of PRPP synthetase activity in cell-free extracts to the apparent rate of ureide export was between 1 and 2. The activities of the enzymes of purne catabolism, xanthine dehydrogenase, uricase, and allantoinase, increased in parallel with the increases in nodule mass and the export of ureides with maximum activities of 13, 119, and 79 micromoles per plant per hour, corresponding with apparent rates of ureide export in the range of 9.5 to 11.9 micromoles per plant per hour. These results demonstrate that there is a ciose association between nitrogen fixation, PRPP synthetase activity, and ureide export in soybeans and support the proposal that recently-fixed nitrogen is utilzed in the de novo synthesis of purnes which are subsequently catabolized to produce the ureides.Based on in vitro measurements of the ATP requirement for the nitrogenase-catalyzed reduction of dinitrogen and whole plant studies of the effects of altering photosynthesis on the rates of N2 fixation in legumes, a number of researchers have suggested that the availability of photosynthetically reduced carbon is the major factor limiting symbiotic nitrogen fixation (9). An estimated 15 to 30%o of the net photosynthate of a plant may be required to

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“…This suggests that the soluble activity was at least in part due to contamination with enzymes released from the particulate components of the nodule. Particulate fractions prepared in this manner contained marker enzymes for proplastids, mitochondria, and microbodies as well as for bacteroids (5) (7,21), and these could contain different complements of enzymic activities and show differential sensitivity of osmotic shock (20).…”

Section: Resultsmentioning

confidence: 99%

De Novo Purine Synthesis in Nitrogen-Fixing Nodules of Cowpea (Vigna unguiculata [L.] Walp.) and Soybean (Glycine max [L.] Merr.)

Atkins¹,

Ritchie²,

Rowe³

et al. 1982

Plant Physiol.

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Partially purified, cell-free extracts from nodules of cowpea (Vigna unguiculata L. Walp. cv. Caloona) and soybean (Glycine mar L. Merr. cv. Bragg) showed high rates of de novo purine nucleotide and purine base synthesis. Activity increased with rates of nitrogen fixation and ureide export during development of cowpea plants; maximum rates (equivalent to 1.2 micromoles N2 per hour per gram fresh nodule) being similar to those of maximum nitrogen fixation (1-2 micromoles N2 per hour per gram fresh nodule). Extracts from actively fixing nodules of a symbiosis not producing ureides, Lupinus albus L. cv. Ultra, showed rates of de novo purine synthesis 0.1% to 0.5% those of cowpea and soybean. Most (70-90%) of the activity was associated with the particulate components of the nodule, but up to 50% was released from this fraction by osmotic shock. The accumulated end products with particulate fractions were inosine monophosphate and aminoimidazole carboxamide ribonucleotide. Further metabolism to purine bases and ureides was restricted to the soluble fraction of the nodule extract. High rates of inosine monophosphate synthesis were supported by glutamine as amide donor, lower rates (10-20%) by ammonia, and negligible rates with asparagine as substrate.The ureides, allantoin and allantoic acid, are formed as major products of nitrogen fixation in a wide range of tropical legumes (8,14). Studies with cell-free extracts of cowpea and soybean nodules have demonstrated that these compounds may be formed from oxidation of purine bases and nucleotides (2,5,22,23) and that this activity is associated with the plant cell cytosol of the central, infected tissue of the nodule (5). A pathway for de novo synthesis of purine nucleotides has been suggested (3) as the source of these purines with currently fixed nitrogen being utilized from the amino groups of glycine and aspartate and the amide group of glutamine. While [1 Clglycine supplied to nodule slices was more effectively metabolized to ureides than was [14Cjglucose or acetate (5), consistent with an active purine pathway, the level of labeling was relatively low. Furthermore, of the eleven enzymes likely to be involved in purine biosynthesis (6)

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Localization of Enzymes of Ureide Biosynthesis in Peroxisomes and Microsomes of Nodules

Cited by 136 publications

References 21 publications

Localization of xanthine dehydrogenase in cowpea root nodules: implications for the interaction between cellular compartments during ureide biogenesis.

Localization of xanthine dehydrogenase in cowpea root nodules: implications for the interaction between cellular compartments during ureide biogenesis.

Enzymes of Purine Biosynthesis and Catabolism in Glycine max

De Novo Purine Synthesis in Nitrogen-Fixing Nodules of Cowpea (Vigna unguiculata [L.] Walp.) and Soybean (Glycine max [L.] Merr.)

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