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. 1983 Aug;72(4):1029–1034. doi: 10.1104/pp.72.4.1029

Role of Inosine Monophosphate Oxidoreductase in the Formation of Ureides in Nitrogen-Fixing Nodules of Cowpea (Vigna unguiculata L. Walp.) 1

Barry J Shelp 1, Craig A Atkins 1
PMCID: PMC1066369  PMID: 16663115

Abstract

Cell-free extracts from nodules of cowpea (Vigna unguiculata L. (Walp.) cv Caloona:Rhizobium strain CB756) prepared in the presence of 15% (v/v) glycerol showed high rates (30 to 60 nanomoles NAD reduced per minute per gram fresh weight nodule) of inosine monophosphate oxidoreductase (EC 1.2.1.14) activity. The enzyme was labile (half-life of activity less than 3 hours) but could be stabilized for up to 18 hours by inclusion of the substrates NAD and inosine monophosphate in the breaking media. Activity showed a broad pH optimum between 8.5 and 9.5, had an apparent Km (inosine monophosphate) of 4 and 12 micromolar at pH 7.5 and 9.0, respectively, and was largely (96%) associated with the plant cell cytosol fraction of the nodule.

Metabolism of [8-14C]inosine monophosphate and [1-14C]glycine by the cell-free system showed two pathways for purine base production from inosine monophosphate, one via xanthosine monophosphate, xanthosine, and xanthine, the other via inosine and hypoxanthine. The proportion of inosine monophosphate utilized by inosine monophosphate oxidoreductase and the xanthine-based pathway was increased from 30% at 0.5 millimolar to 80% at 0.01 millimolar inosine monophosphate. The data are interpreted to indicate that in vivo inosine monophosphate oxidation rather than dephosphorylation is the predominant metabolic route leading to ureide synthesis and that inosine monophosphate provides the link between de novo purine nucleotide synthesis in the plastid and ureide production in the plant cell cytosol.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Atkins C. A., Ritchie A., Rowe P. B., McCairns E., Sauer D. De Novo Purine Synthesis in Nitrogen-Fixing Nodules of Cowpea (Vigna unguiculata [L.] Walp.) and Soybean (Glycine max [L.] Merr.). Plant Physiol. 1982 Jul;70(1):55–60. doi: 10.1104/pp.70.1.55. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Boland M. J., Schubert K. R. Purine biosynthesis and catabolism in soybean root nodules: incorporation of 14C from 14CO2 into xanthine. Arch Biochem Biophys. 1982 Feb;213(2):486–491. doi: 10.1016/0003-9861(82)90574-4. [DOI] [PubMed] [Google Scholar]
  3. Clonis Y. D., Lowe C. R. Affinity chromatography on immobilised triazine dyes. Studies on the interaction with multinucleotide-dependent enzymes. Biochim Biophys Acta. 1981 May 14;659(1):86–98. doi: 10.1016/0005-2744(81)90273-4. [DOI] [PubMed] [Google Scholar]
  4. Fujihara S., Yamaguchi M. Effects of Allopurinol [4-Hydroxypyrazolo(3,4-d)Pyrimidine] on the Metabolism of Allantoin in Soybean Plants. Plant Physiol. 1978 Jul;62(1):134–138. doi: 10.1104/pp.62.1.134. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Guranowski A. Nucleoside phosphotransferase from yellow lupin seedling cotyledons. Biochim Biophys Acta. 1979 Jul 11;569(1):13–22. doi: 10.1016/0005-2744(79)90076-7. [DOI] [PubMed] [Google Scholar]
  6. Guranowski A. Purine catabolism in plants : purification and some properties of inosine nucleosidase from yellow lupin (lupinus luteus L.) seeds. Plant Physiol. 1982 Aug;70(2):344–349. doi: 10.1104/pp.70.2.344. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Herridge D. F., Atkins C. A., Pate J. S., Rainbird R. M. Allantoin and Allantoic Acid in the Nitrogen Economy of the Cowpea (Vigna unguiculata [L.] Walp.). Plant Physiol. 1978 Oct;62(4):495–498. doi: 10.1104/pp.62.4.495. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. MAGASANIK B., MOYED H. S., GEHRING L. B. Enzymes essential for the biosynthesis of nucleic acid guanine; inosine 5'-phosphate dehydrogenase of Aerobacter aerogenes. J Biol Chem. 1957 May;226(1):339–350. [PubMed] [Google Scholar]
  9. Pate J. S., Atkins C. A., White S. T., Rainbird R. M., Woo K. C. Nitrogen Nutrition and Xylem Transport of Nitrogen in Ureide-producing Grain Legumes. Plant Physiol. 1980 May;65(5):961–965. doi: 10.1104/pp.65.5.961. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. TURNER J. F., KING J. E. Inosine 5'-phosphate dehydrogenase of pea seeds. Biochem J. 1961 Apr;79:147–151. doi: 10.1042/bj0790147. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Triplett E. W., Blevins D. G., Randall D. D. Allantoic Acid Synthesis in Soybean Root Nodule Cytosol via Xanthine Dehydrogenase. Plant Physiol. 1980 Jun;65(6):1203–1206. doi: 10.1104/pp.65.6.1203. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Woo K. C., Atkins C. A., Pate J. S. Biosynthesis of Ureides from Purines in a Cell-free System from Nodule Extracts of Cowpea [Vigna unguiculata (L) Walp.]. Plant Physiol. 1980 Oct;66(4):735–739. doi: 10.1104/pp.66.4.735. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Woo K. C. Ureide Synthesis in a Cell-Free System from Cowpea (Vigna unguiculata [L.] Walp.) Nodules : STUDIES WITH O(2), pH, AND PURINE METABOLITES. Plant Physiol. 1981 Jun;67(6):1156–1160. doi: 10.1104/pp.67.6.1156. [DOI] [PMC free article] [PubMed] [Google Scholar]

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