Tissue and subcellular localization of enzymes of arginine metabolism in Pisum sativum

Taylor, A. A.; Stewart, G. R.

doi:10.1016/0006-291x(81)91586-2

Cited by 66 publications

(31 citation statements)

References 23 publications

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“…Therefore, the cloned A. thaliana ␦-OAT cDNA does not seem to encode an isoenzyme localized in a distinct subcellular compartment. This is in agreement with the subcellular localization of the plant ␦-OAT by measurement of its activity in isolated mitochondria (Taylor and Stewart, 1981;Polacco and Holland, 1993) and with the fact that arginase, the other enzyme of Arg catabolism, is also localized in this organelle (Taylor and Stewart, 1981).…”

Section: Discussionsupporting

confidence: 87%

Isolation of the Ornithine-δ-Aminotransferase cDNA and Effect of Salt Stress on Its Expression inArabidopsis thaliana1

et al. 1998

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To evaluate the relative importance of ornithine (Orn) as a precursor in proline (Pro) synthesis, we isolated and sequenced a cDNA encoding the Orn-␦-aminotransferase (␦-OAT) from Arabidopsis thaliana. The deduced amino acid sequence showed high homology with bacterial, yeast, mammalian, and plant sequences, and the N-terminal residues exhibited several common features with a mitochondrial transit peptide. Our results show that under both salt stress and normal conditions, ␦-OAT activity and mRNA in young plantlets are slightly higher than in older plants. This appears to be related to the necessity to dispose of an easy recycling product, glutamate. Analysis of the expression of the gene revealed a close association with salt stress and Pro production. In young plantlets, free Pro content, ⌬ 1 -pyrroline-5-carboxylate synthase mRNA, ␦-OAT activity, and ␦-OAT mRNA were all increased by salt-stress treatment. These results suggest that for A. thaliana, the Orn pathway, together with the glutamate pathway, plays an important role in Pro accumulation during osmotic stress. Conversely, in 4-week-old A. thaliana plants, although free Pro level also increased under salt-stress conditions, the ␦-OAT activity appeared to be unchanged and ␦-OAT mRNA was not detectable. ⌬ 1 -pyrroline-5-carboxylate synthase mRNA was still induced at a similar level. Therefore, for the adult plants the free Pro increase seemed to be due to the activity of the enzymes of the glutamate pathway.

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Section: Discussionsupporting

confidence: 87%

Isolation of the Ornithine-δ-Aminotransferase cDNA and Effect of Salt Stress on Its Expression inArabidopsis thaliana1

et al. 1998

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“…The pine polypeptide, like other d-OATs in plants and mammals, has a putative N-terminal transit peptide for mitochondrial targeting. This structural feature is consistent with the localization of d-OAT and arginase activities in plant isolated mitochondria (Taylor and Stewart, 1981;Goldraij and Polacco, 2000) and the recently published targeting of d-OAT/GFP chimeric protein to the mitochondria in Arabidopsis (Funck et al, 2008). Arginase and d-OAT enzymes have also been located in the mitochondria of mammalian cells (Levillain et al, 2004).…”

Section: Discussionsupporting

confidence: 86%

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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“…36 and 68). Three (acetylornithine aminotransferase, ornithine carbamoyltransferase, and argininosuccinate lyase) are implicated in the synthesis of arginine, catalyzing the fourth, sixth, and eighth (last) step of the pathway, respectively (37). Interestingly, possibly reflecting activation by redox, sulfhydryl compounds were reported to increase the activity of ornithine carbamoyltransferase (38).…”

Section: Identification Of Members Of the Ferredoxin͞trx System And Smentioning

confidence: 99%

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

Balmer

Vensel

Cai

et al. 2006

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

160

137

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A growing number of processes throughout biology are regulated by redox via thiol-disulfide exchange. This mechanism is particularly widespread in plants, where almost 200 proteins have been linked to thioredoxin (Trx), a widely distributed small regulatory disulfide protein. The current study extends regulation by Trx to amyloplasts, organelles prevalent in heterotrophic plant tissues that, among other biosynthetic activities, catalyze the synthesis and storage of copious amounts of starch. Using proteomics and immunological methods, we identified the components of the ferredoxin͞Trx system (ferredoxin, ferredoxin-Trx reductase, and Trx), originally described for chloroplasts, in amyloplasts isolated from wheat starchy endosperm. Ferredoxin is reduced not by light, as in chloroplasts, but by metabolically generated NADPH via ferredoxin-NADP reductase. However, once reduced, ferredoxin appears to act as established for chloroplasts, i.e., via ferredoxinTrx reductase and a Trx (m-type). A proteomics approach in combination with affinity chromatography and a fluorescent thiol probe led to the identification of 42 potential Trx target proteins, 13 not previously recognized, including a major membrane transporter (Brittle-1 or ADP-glucose transporter). The proteins function in a range of processes in addition to starch metabolism: biosynthesis of lipids, amino acids, and nucleotides; protein folding; and several miscellaneous reactions. The results suggest a mechanism whereby light is initially recognized as a thiol signal in chloroplasts, then as a sugar during transit to the sink, where it is converted again to a thiol signal. In this way, amyloplast reactions in the grain can be coordinated with photosynthesis taking place in leaves.redox regulation ͉ target proteins ͉ ferredoxin-thioredoxin reductase O ur understanding of the function of the regulatory disulfide protein thioredoxin (Trx) has increased dramatically in the past few years, with the advent of new methodologies. Recent approaches make it possible to identify proteins linked to Trx by combining proteomics with affinity chromatography (1) or thiol probes (2-4). These capabilities have defined an extended role of Trx in chloroplasts (1, 5) and helped elucidate its function in other plant systems: mitochondria (6), seeds (2,3,7,8), and seedlings (4, 9). Currently almost 200 proteins appear to be linked to Trx in plants (10). One major organelle that has been neglected, however, is the amyloplast, a plastid of heterotrophic tissues that performs a wide range of biosynthetic reactions, including the synthesis and storage of abundant quantities of starch.To help fill this gap, we have applied proteomic and immunological approaches to investigate the occurrence and function of Trx in amyloplasts. We now report evidence that amyloplasts isolated from wheat starchy endosperm resemble chloroplasts in containing a complete ferredoxin͞Trx system composed of ferredoxin, ferredoxin-Trx reductase (FTR), and Trx (m-type). Application of affinity chromatography and fl...

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Tissue and subcellular localization of enzymes of arginine metabolism in Pisum sativum

Cited by 66 publications

References 23 publications

Isolation of the Ornithine-δ-Aminotransferase cDNA and Effect of Salt Stress on Its Expression inArabidopsis thaliana1

Isolation of the Ornithine-δ-Aminotransferase cDNA and Effect of Salt Stress on Its Expression inArabidopsis thaliana1

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

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

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