l-Ornithine:2-Oxoacid Aminotransferase from Squash (<i>Cucurbita pepo</i>, L.) Cotyledons

Lu, Ti-Shen; Mazelis, Mendel

doi:10.1104/pp.55.3.502

Cited by 36 publications

(13 citation statements)

References 6 publications

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“…3). The pH and temperature optima of OAT observed in the present investigation (Figs 1-2) was similar to the enzyme from other sources (Sudi and Denes 1967, Mazelis and Fowden 1969, Lu and Mazelis 1975. Though differences in pH and temperature responses of OAT from SR3P6-2 and Prakash were minor, these do indicate differences in enzyme properties.…”

Section: Effect Of Chloridessupporting

confidence: 68%

“…The Km for the ct-ketoglutarate was in general similar (Vogel and Kopac 1960), but that for L-ornithine was relatively higher for the Brass!ca OAT compared to other plants (Sudi and Denes 1967;Fowden 1969, Lu andMazelis 1975). Km for L-ornithine was re- (Splittstoesser and Fowden 1973) and 6.3 mmol-dm -3 for ot-ketoglutarate for cucurbita OAT (Lu and Mazelis 1975). Under salt-stress, substrates for proline biosynthesis are likely to be limiting.…”

Section: Effect Of Chloridesmentioning

confidence: 91%

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Properties of partially purified leaf ornithine aminotransferase of Brassica juncea under salt stress

Madan

Nainawatee

2000

Acta Physiol Plant

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Properties of the partially purified L-ornithine: 2-oxoacid aminotransferase (EC 2.6.1.13) of leaves of Brassica juncea salt tolerant somaclone SR3P6-2 and its parent cv. Prakash were studied. The enzyme from the somaclone SR3P6-2 was relatively more efficient in terms of its Kin, Vmax, and Ea (activation energy) and required higher levels of chlorides for inhibition as compared to the enzyme from the parent cv. Prakash. These results suggest some salt-stress related changes in the enzyme.

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Section: Effect Of Chloridessupporting

confidence: 68%

Section: Effect Of Chloridesmentioning

confidence: 91%

Properties of partially purified leaf ornithine aminotransferase of Brassica juncea under salt stress

Madan

Nainawatee

2000

Acta Physiol Plant

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“…OAT activity was determined according to Lu and Mazelis. 17 A 1 g portion of milled beans (mesh 60) and 10 ml of cold acetone (−15 • C) were homogenised at 4 • C and filtered through a Buchner funnel using Whatman No 4 paper. The retained powder (acetone extract) was dried at room temperature and stored at −15 • C. The acetone extract and 20 volumes of 10 mM potassium phosphate buffer (pH 7.2) were agitated for 30 min at 4 • C, then centrifuged at 11 400 × g for 20 min, and the supernatant was stored at −20 • C for further analysis.…”

Section: Proline and Ornithine Concentrations And Ornithine Amino Tramentioning

confidence: 99%

Effect of drought on polyamine metabolism, yield, protein content and in vitro protein digestibility in tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) bean seeds

et al. 2003

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The objective of the present study was to investigate the effect of drought on the metabolism of proline, ornithine and polyamines, and the enzymes involved in their synthesis and degradation, in tepary and common bean seeds. Furthermore, the effect on seed yield, protein content and in vitro protein digestibility was also studied. Genotypes of tepary bean (Phaseolus acutifolius) used were: PI-301-801 from Nicaragua; G-400-35 from Oaxaca, Mexico; L-242-24 and L-242-36 from Sonora, Mexico; L-172 from Arizona, USA; and the common bean (Phaseolus vulgaris) variety Flor de Mayo Bajío (FMB) from Mexico. The cultivars were grown in a greenhouse under controlled temperature, light and humidity. Water content in plants (WCP) decreased when irrigation was stopped (1 and 2 weeks after blooming). Common bean had the lowest WCP value (73.75%), while the best genotypes were PI-301-801 (91.62%), G-400-35 (88.70%) and L-242-24 (85.73%). Tepary bean plants had superior water absorption capacity, which helped to increase yield. De novo synthesis of drought proteins may explain the increased protein content present under drought conditions. The results suggest that water stress induced ornithine amino transferase activity and ornithine concentration. Proline also increased under drought conditions (p < 0.05). Genotypes L-242-24 and G-400-35, which had the highest yield, also had a major concentration of polyamines under water stress. The results also suggest that arginase activity participated in amino acid synthesis such as ornithine and, consequently, in the protein concentration under water stress. Genotypes G-400-35 and L-242-24 are good alternatives for cultivation in arid zones.

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“…Composition of reaction mixture was according to Lu and Mazelis (14). The reaction was stopped by adding 0.8 ml of 17.5% (v/v) HCI04.…”

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confidence: 99%

Arginine Catabolism in the Cotyledons of Developing and Germinating Pea Seeds

Ruiter¹,

Kollöffel²

1983

Plant Physiol.

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Arginine is the predominant free amino acid in the cotyledons of developing seeds of Pisum sativum L. cv Marzia. Breakdown of arginine was measured by injecting L-Iguanido-4Cjarginine into detached cotyledons. Cotyledons ofdeveloping seeds showed a low rate of 'C02 evolution whereas a much higher rate of '4("2 evolution was measured from cotyledons of seeds 4 days after the onset of germination. Arginine is an important N-storage compound in many higher plants. In developing pea seeds (4) and cotton seeds (5), arginine formation is considered to be located in the cotyledons themselves.The first steps of arginine degradation are catalyzed by arginase, OAT2, and urease yielding C02, NH3, and GSA. This pathway appears to be related to the transfer ofarginine-nitrogen to other amino acids and amides (18,27 A powder sample equivalent to 10 cotyledons was extracted with 80% (v/v) ethanol. After removal of ethanol by rotationevaporation, water was added to the residue to a final volume of 50 ml. Four ml of this extract was then shaken'with 4 ml CHC13 and centrifuged 10 min at 1000g. The water phase was carefully removed. Proteins in the water phase were precipitated by adding 1 ml of 10% (w/v) sulfosalicylic acid. The supematant obtained after precipitation was called the amino acid fraction. Arginine was determined by using an amino acid autoanalyzer (Biotronic LC 6000 E).Urea. Urea in the amino acid fraction was measured colorimetrically with diacetyl monoxime and thiosemicarbazide (21). Measurements were corrected for non-urea response caused by citrulline and arginine. Presence of urea from 0.05 ,mol/cotyledon can be demonstrated by using this assay.Protein Arginine. Proteins were extracted (1) from powder samples equivalent to five or more cotyledons, dependent on the stage of development. After grinding the sample with 50 mm Na2B407 and removal of cell debris by centrifugation 10 min-at 1000g, the proteins were collected by TCA precipitation (final concentration, 10% (w/v) TCA). The precipitate was washed twice with 5% (w/v) TCA and then twice with redistilled acetone. Protein hydrolysis occurred in 6 N HCI under N2 for 16 h. After removal of HCI under a stream of dry air at 100°C, arginine was determined colorimetrically (28) in the diluted (200 x) hydrolysate. The results concurred with determinations using an amino acid autoanalyzer.Nitrogen. The nitrogen content ofthe cotyledons, the extracted proteins, and the amino acid fractions were determined by using an elemental analyzer (Carlo Erba, model 1106

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l-Ornithine:2-Oxoacid Aminotransferase from Squash (Cucurbita pepo, L.) Cotyledons

Cited by 36 publications

References 6 publications

Properties of partially purified leaf ornithine aminotransferase of Brassica juncea under salt stress

Properties of partially purified leaf ornithine aminotransferase of Brassica juncea under salt stress

Effect of drought on polyamine metabolism, yield, protein content and in vitro protein digestibility in tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) bean seeds

Arginine Catabolism in the Cotyledons of Developing and Germinating Pea Seeds

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