Biochemical characterization, homology modeling and docking studies of ornithine δ-aminotransferase—an important enzyme in proline biosynthesis of plants

Sekhar, P. Nataraj; Amrutha, R. Naga; Sangam, S.; Verma, Desh Pal S.; Kishor, P. B. Kavi

doi:10.1016/j.jmgm.2007.04.006

Cited by 37 publications

(24 citation statements)

References 32 publications

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“…In both cases no Michaelis-Menten kinetics were obtained, suggesting a positive cooperative behavior of the enzyme (n 5 1.5 for 2-oxoglutarate and n 5 2.3 for Orn). The measured kinetic values (S 0.5 5 0.8 mM for 2-oxoglutarate and S 0.5 5 6.3 mM for Orn) are in the range of those previously reported (Drejer and Schousboe, 1984;Sekhar et al, 2007). …”

Section: Recombinant Psdoat Protein Exhibits D-oat Activitysupporting

confidence: 84%

Molecular and Functional Analyses Support a Role of Ornithine-δ-Aminotransferase in the Provision of Glutamate for Glutamine Biosynthesis during Pine Germination

et al. 2008

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We report the molecular characterization and functional analysis of a gene (PsdOAT) from Scots pine (Pinus sylvestris) encoding Orn-d-aminotransferase (d-OAT; EC 2.6.1.13), an enzyme of arginine metabolism. The deduced amino acid sequence contains a putative N-terminal signal peptide for mitochondrial targeting. The polypeptide is similar to other d-OATs from plants, yeast, and mammals and encoded by a single-copy gene in pine. PsdOAT encodes a functional d-OAT as determined by expression of the recombinant protein in Escherichia coli and analysis of the active enzyme. The expression of PsdOAT was undetectable in the embryo, but highly induced at early stages of germination and seedling development in all different organs. Transcript levels decreased in later developmental stages, although an increase was observed in lignified stems of 90-d-old plants. An increase of d-OAT activity was observed in germinating embryos and seedlings and appears to mirror the observed alterations in PsdOAT transcript levels. Similar expression patterns were also observed for genes encoding arginase and isocitrate dehydrogenase. Transcripts of PsdOAT and the arginase gene were found widely distributed in different cell types of pine organs. Consistent with these results a metabolic pathway is proposed for the nitrogen flow from the megagametophyte to the developing seedling, which is also supported by the relative abundance of free amino acids in embryos and seedlings. Taken together, our data support that d-OAT plays an important role in this process providing glutamate for glutamine biosynthesis during early pine growth.

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Section: Recombinant Psdoat Protein Exhibits D-oat Activitysupporting

confidence: 84%

Molecular and Functional Analyses Support a Role of Ornithine-δ-Aminotransferase in the Provision of Glutamate for Glutamine Biosynthesis during Pine Germination

et al. 2008

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“…28 As has been mentioned above, docking studies with the mothbean OAT model revealed interactions that are involved in binding of competitive inhibitors. 17 Based on the interaction energies, isoleucine and valine were the best enzyme ligands from this group. Valine showed even more favorable binding energy than ornithine itself.…”

Section: Three-dimensional Structurementioning

confidence: 95%

“…4 Recombinant mothbean OAT was found to be inhibited significantly by isoleucine, valine and serine, whereas proline showed no apparent effect (at a concentration of 1 mM of each). 17 Ten years ago, a cDNA encoding OAT from Arabidopsis thaliana was obtained and sequenced. 8 At present, a number of other plant OAT sequences (e.g., from aquilegia, barrel medic, grape, maize, pine, potato, rice, sorghum and soybean) are available in public DNA and protein databases.…”

Section: Plant Ornithine δ-Aminotransferasesmentioning

confidence: 99%

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Ornithine δ-aminotransferase

Stránská

Kopečný²,

Tylichová

et al. 2008

Plant Signaling & Behavior

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This review deals with biochemical and physiological aspects of plant ornithine d-aminotransferase (OAT, EC 2.6.1.13). OAT is a mitochondrial enzyme containing pyridoxal-5'-phosphate as a cofactor, which catalyzes the conversion of L-ornithine to L-glutamate gamma-semialdehyde using 2-oxoglutarate as a terminal amino group acceptor. It has been described in humans, animals, insects, plants and microorganisms. Based on the crystal structure of human OAT, both substrate binding and reaction mechanism of the enzyme are well understood. OAT shows a large structural and mechanistic similarity to other enzymes from the subgroup III of aminotransferases, which transfer an amino group from a carbon atom that does not carry a carboxyl function. In plants, the enzyme has been implicated in proline biosynthesis and accumulation (via pyrroline-5-carboxylate), which represents a way to regulate cellular osmolarity in response to osmotic stress. However, the exact metabolic pathway involving OAT remains a subject of controversy.

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“…Proline is synthesized from glutamic acid by Δ1-pyrroline-5-carboxylate (P5C), by two successive reductions catalyzed by the enzymes Δ'-pyrroline-5-carboxylate synthase (P5CS) and Δ'-pyrroline-5-carboxylate reductase (P5CR) (Sekhar et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Osmotic stress on genetically transformed tobacco plant seeds

et al. 2017

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-Salinity and water deficit limit the productivity of several crops; thus, studies related to the genetic transformation of seeds in a model plant, such as tobacco, can be an alternative to minimize negative impacts caused by environmental conditions. The purpose of this work was to evaluate the tolerance to osmotic stress of seeds from genetically transformed tobacco plants, with the introduction of the proline-synthesizer gene (p5csf129a), under salinity and water deficit conditions. To do so, five events with differences in proline content were selected, ranging from 0.70 to 10.47 µmoles.g -1 of fresh mass. The used saline concentrations were: zero (distilled water); 50; 100; 150 and 200 mmol.L -1 of NaCl, whereas for the water deficit, simulated with PEG 6000, the following osmotic potentials were used: zero (distilled water); -0.2; -0.4; -0.6 and -0.8 MPa. Each tested treatment was evaluated through germination, first germination count and germination speed index tests. It is possible to conclude that seeds from genetically transformed tobacco plants with overexpression of the gene p5csf129a, a proline synthesizer, are more tolerant to osmotic stresses. Tabacco seeds with a proline content of 10.47 µmol.g -1 showed a better perfomance, revealing higher physiological potential.

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Biochemical characterization, homology modeling and docking studies of ornithine δ-aminotransferase—an important enzyme in proline biosynthesis of plants

Cited by 37 publications

References 32 publications

Molecular and Functional Analyses Support a Role of Ornithine-δ-Aminotransferase in the Provision of Glutamate for Glutamine Biosynthesis during Pine Germination

Molecular and Functional Analyses Support a Role of Ornithine-δ-Aminotransferase in the Provision of Glutamate for Glutamine Biosynthesis during Pine Germination

Ornithine δ-aminotransferase

Osmotic stress on genetically transformed tobacco plant seeds

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