Enzymes of nitrogen metabolism in legume nodules: Partial purification and properties of the aspartate aminotransferases from lupine nodules

Reynolds, Paul H. S.; Boland, Michael J.; Farnden, Kevin J. F.

doi:10.1016/0003-9861(81)90310-6

Cited by 50 publications

(48 citation statements)

References 21 publications

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“…Two forms of AAT (AAT-1 and AAT-2) have been identified in alfalfa root nodules (4). This is similar to the prior finding of two forms of AAT (AAT-Pl and AAT-P2) in lupine (Lupinus angustifolius L.) root nodules (13,14). Egli et al (1) showed that AAT in vitro specific activity and relative amounts ofAAT enzyme protein increase in alfalfa nodules during early stages of nodule development from 7 to 17 DAP.…”

supporting

confidence: 72%

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Aspartate Aminotransferase in Alfalfa Root Nodules

Farnham¹,

Griffith²,

Miller³

et al. 1990

Plant Physiol.

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Aspartate aminotransferase (AAT) plays an important role in nitrogen metabolism in all plants and is particularly important in the assimilation of fixed N derived from the legume-Rhizobium symbiosis. Two isozymes of AAT (AAT-1 and AAT-2) occur in alfalfa (Medicago sativa L.). Antibodies against alfalfa nodule AAT-2 do not recognize AAT-1, and these antibodies were used to study AAT-2 expression in different tissues and genotypes of alfalfa and also in other legume and nonlegume species. Rocket immunoelectrophoresis indicated that nodules of 38-day-old alfalfa plants contained about eight times more AAT-2 than did nodules of 7-day-old plants, confirming the nodule-enhanced nature of this isozyme. AAT-2 was estimated to make up 16, 15, 5, and 8 milligrams per gram of total soluble protein in mature nodules, roots, stems, and leaves, respectively, of effective N2-fixing alfalfa. The concentration of AAT-2 in nodules of ineffective non-N2-fixing alafalfa genotypes was about 70% less than that of effective nodules. Westem blots of soluble protein from nodules of nine legume species indicated that a 40-kilodalton polypeptide that reacts strongly with AAT-2 antibodies is conserved in legumes. Nodule AAT-2 immunoprecipitation data suggested that amide-and ureide-type legumes may differ in expression and regulation of the enzyme. In addition, Westem blotting and immunoprecipitations of AAT activity demonstrated that antibodies against alfalfa AAT-2 are highly cross-reactive with AAT enzyme protein in leaves of soybean (Glycine max L.), wheat (Triticum aestivum L.), and maize (Zea mays L.) and in roots of maize, but not with AAT in soybean and wheat roots. Results from this study indicate that AAT-2 is structurally conserved and localized in similar tissues among diverse species. AAT3 (EC 2.6.1.1) plays an important role in nitrogen and '

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confidence: 72%

“…Distinct isozymes of AAT occur in legumes (4, [13][14][15] and nonlegumes (5,11,16,21). Two forms of AAT (AAT-1 and AAT-2) have been identified in alfalfa root nodules (4).…”

mentioning

confidence: 99%

Aspartate Aminotransferase in Alfalfa Root Nodules

Farnham¹,

Griffith²,

Miller³

et al. 1990

Plant Physiol.

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“…In plants, AAT plays an essential role in (a) the assimilation of reduced nitrogen into aspartic acid and asparagine, particularly in legume root nodules (9,25); (b) the transfer of fixed carbon from mesophyll cells to bundle sheath cells in C4 plants (20,31); and (c) the transfer of reducing equivalents to chloroplasts, mitochondria, and peroxisomes through a malate-aspartate shuttle (13). Cytosolic, mitochondrial, and plastid forms of the plant enzyme have been documented and suggested to be controlled by different genetic loci (13).…”

mentioning

confidence: 99%

“…Root nodules of alfalfa, pea, and lupine, which mainly assimilate and transport symbiotically fixed nitrogen as aspartate and asparagine, are particularly rich sources of AAT activity (4,9,25). Multiple forms of the enzyme have been purified from both alfalfa (4,9) and lupine (25).…”

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Aspartate Aminotransferase in Effective and Ineffective Alfalfa Nodules

Gantt¹,

Larson

Farnham

et al. 1992

Plant Physiol.

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Aspartate aminotransferase (AAT) is a key plant enzyme affecting nitrogen and carbon metabolism, particularly in legume root nodules and leaves of C4 species. To ascertain the molecular genetic characteristics and biochemical regulation of AAT, we have isolated a cDNA encoding the nodule-enhanced AAT (AAT-2) of alfalfa (Medicago sativa L.) by screening a root nodule cDNA expression library with antibodies. Complementation of an Escherichia coRi AAT mutant with the alfalfa nodule AAT-2 cDNA verified the identity of the clone. The deduced amino acid sequence of alfalfa AAT-2 is 53 and 47% identical to animal mitochondrial and cytosolic AATs, respectively. The deduced molecular mass of AAT-2 is 50,959 daltons, whereas the mass of purified AAT-2 is about 40 kilodaltons as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the protein's N-terminal domain (amino acids 1-59) contains many of the characteristics of plastid-targeting peptides. We postulate that AAT-2 is localized to the plastid. Southem blot analysis suggests that AAT-2 is encoded by a small, multigene family. The expression of AAT-2 mRNA in nodules is severalfold greater than that in either leaves or roots. Northem and western blots showed that expression of AAT activity during effective nodule development is accompanied by a sevenfold increase in AAT-2 mRNA and a comparable increase in enzyme protein. By contrast, plant-controlled ineffective nodules express AAT-2 mRNA at much lower levels and have little to no AAT-2 enzyme protein. Expression of root nodule AAT-2 appears to be regulated by at least two events: the first is independent of nitrogenase activity; the second is associated with nodule effectiveness. AAT2 (EC 2.6.1.1) catalyzes the reversible reaction, glutamate + oxaloacetate <-+ aspartate + a-ketoglutarate. The '

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Recombinant Expression, Purification, and Characterization of Three Isoenzymes of Aspartate Aminotransferase fromArabidopsis thaliana

Wilkie

Warren

1998

Protein Expression and Purification

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Enzymes of nitrogen metabolism in legume nodules: Partial purification and properties of the aspartate aminotransferases from lupine nodules

Cited by 50 publications

References 21 publications

Aspartate Aminotransferase in Alfalfa Root Nodules

Aspartate Aminotransferase in Alfalfa Root Nodules

Aspartate Aminotransferase in Effective and Ineffective Alfalfa Nodules

Recombinant Expression, Purification, and Characterization of Three Isoenzymes of Aspartate Aminotransferase fromArabidopsis thaliana

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