New evidence for the metabolic conversion of aspartate-4-^<14>C to glutamine-1-^<14>C during the initial period of ammonia assimilation in the roots of barley plants
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概要
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Metabolic conversion of aspartate was investigated in roots of barley plants fed a 30-min pulse of aspartate-4-^<14>C, followed by transfer to an ammonia or nitrate medium for 1 hr. Glutamate was the predominant labeled amino acid after the pulse; whereas, glutamine was after ammonia assimilation. Each label appeared almost entirely at the C-1 position. The organic acid fraction was also labeled with ^<14>C. Negligible labeling of asparagine showed that it was not a primary product of ammonia assimilation. The data demonstrated that aspartate-4-^<14>C was transformed into glutamate-1-^<14>C by the tricarboxylic acid cycle mechanism, with glutamate being converted to glutamine-1-^<14>C during ammonia assimilation. The physiological significance of this metabolic conversion in plant metabolism is discussed. This conversion plays an important role in preventing a drop in the oxalacetate level when a-ketoglutarate has been drained off by rapid synthesis of glutamate and glutamine during the initial period of ammonia assimilation. This paper also presents, for the first time, evidence for the existence of a new pathway, named the "aspartate-glutamine pathway", in higher plants.
- 日本植物生理学会の論文
著者
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OJI Yoshikiyo
Department of Agricultural Chemistry, Faculty of Agriculture, Kobe University
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Oji Yoshikiyo
Department Of Agricultural Chemistry Faculty Of Agriculture Kobe University
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Izawa Goro
Department of Agricultural Chemistry, Faculty of Agriculture, Kobe University
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Izawa Goro
Department Of Agricultural Chemistry Faculty Of Agriculture Kobe University
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