The Biosynthesis of Dicarboxylic Amino Acids and Enzymic Transformations of Amides in Plants

Wl, Kretovich

doi:10.1002/9780470122655.ch10

Cited by 3 publications

(1 citation statement)

References 28 publications

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“…Prior evidence of the ω-amidase pathway in plants includes reports related to GTK function. Crude plant extracts were found to synthesize 2OGM ( Kretovich, 1958 ), whereas extracts of peas ( Pisum sativum ) were found to contain active GTK ( Ireland and Joy, 1983 ). GTK protein was identified in the pea chloroplast proteome ( Bayer et al, 2011 ).…”

Section: Introductionmentioning

confidence: 99%

The intermediate in a nitrate-responsive ω-amidase pathway in plants may signal ammonium assimilation status

2022

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A metabolite of ammonium assimilation was previously theorized to be involved in the coordination of the overall nitrate response in plants. Here we show that 2-hydroxy-5-oxoproline, made by transamination of glutamine, the first product of ammonium assimilation, may be involved in signaling a plant’s ammonium assimilation status. In leaves, 2-hydroxy-5-oxoproline met four foundational requirements to be such a signal. First, when it was applied to foliage, enzyme activities of nitrate reduction and ammonium assimilation increased; the activities of key tricarboxylic acid cycle-associated enzymes that help to supply carbon skeletons for amino acid synthesis also increased. Second, its leaf pools increased as nitrate availability increased. Third, the pool size of its precursor, Gln, reflected ammonium assimilation rather than photorespiration. Fourth, it was widely conserved among monocots, dicots, legumes and nonlegumes and in plants with C3 or C4 metabolism. Made directly from the first product of ammonium assimilation, 2-hydroxy-5-oxoproline acted as a nitrate uptake stimulant. When 2-hydroxy-5-oxoproline was provided to roots, the plant’s nitrate uptake rate approximately doubled. Plants exogenously provided with 2-hydroxy-5-oxoproline to either roots or leaves accumulated greater biomass. A model was constructed that includes proposed roles of 2-hydroxy-5-oxoproline as a signal molecule of ammonium assimilation status in leaves, as a stimulator of nitrate uptake by roots and nitrate downloading from the xylem. In summary, a glutamine metabolite made in the ω-amidase pathway stimulated nitrate uptake by roots and was likely to be a signal of ammonium assimilation status in leaves. A chemical synthesis method for 2-hydroxy-5-oxoproline was also developed.

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Section: Introductionmentioning

confidence: 99%

The intermediate in a nitrate-responsive ω-amidase pathway in plants may signal ammonium assimilation status

2022

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Note on study of the sporulation of fungi: endotrophic sporulation in the genusPenicillium

Jičínská

1968

Folia Microbiol

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Enzymes in cancer. Asparaginase from chicken liver

Ohnuma¹,

Bergel²,

Bray³

1967

Biochemical Journal

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1. A procedure for partial purification of asparaginase from chicken liver is presented. 2. The bulk of the enzyme is located in the soluble fraction of chicken liver. 3. Molecular weights of chicken-liver asparaginase and of the guinea-pig serum enzyme, estimated by gel filtration, were 306000 and 210000 respectively. The Michaelis constants (K(m)) at 37 degrees and pH8.5 were 6.0x10(-5)m and 7.2x10(-5)m respectively. 4. At 50 degrees the chicken-liver enzyme was moderately stable, some activity being lost by aggregation; in dilute electrolyte solutions the activity rapidly diminished. 5. The anti-lymphoma effect of guinea-pig serum in mice carrying the 6C3HED tumour was confirmed. Chicken-liver asparaginase also showed an effect but in this case the enzyme preparation had to be administered repeatedly. 6. Guinea-pig serum asparaginase was stable for several days in mouse blood, after intraperitoneal injection, whereas chicken-liver asparaginase rapidly disappeared. 7. Aspartic acid beta-hydrazide was shown to be a competitive inhibitor of chicken-liver asparaginase with K(i) approx. 5.6x10(-4)m. In mice it produced an anti-lymphoma effect, as reported previously.

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The Biosynthesis of Dicarboxylic Amino Acids and Enzymic Transformations of Amides in Plants

Cited by 3 publications

References 28 publications

The intermediate in a nitrate-responsive ω-amidase pathway in plants may signal ammonium assimilation status

The intermediate in a nitrate-responsive ω-amidase pathway in plants may signal ammonium assimilation status

Note on study of the sporulation of fungi: endotrophic sporulation in the genusPenicillium

Enzymes in cancer. Asparaginase from chicken liver

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