Department of Biology, Carleton University, Ottawa, Canada K1S 5B6.
Plant Physiol. 1977 May;59(5):920-4. doi: 10.1104/pp.59.5.920.
Short term (2-hour) incorporation of nitrogen from nitrate, glutamine, or asparagine was studied by supplying them as unlabeled ((14)N) tracers to growing pea (Pisum sativum L.) leaves, which were previously labeled with (15)N, and then following the elimination of (15)N from various amino components of the tissue. Most components had active and inactive pools. Ammonia produced from nitrate was assimilated through the amide group of glutamine. When glutamine was supplied, its nitrogen was rapidly transferred to glutamic acid, asparagine, and other products, and there was some transfer to ammonia. Nitrogen from asparagine was widely distributed into ammonia and amino compounds. There was a rapid direct transfer to glutamine, which did not appear to involve free ammonia. Alanine nitrogen could be derived directly from asparagine, probably by transamination. Homoserine was synthesized in substantial amounts from all three nitrogen sources. Homoserine appears to derive nitrogen more readily from asparagine than from free aspartic acid. A large proportion of the pool of gamma-aminobutyric acid turned over, and was replenished with nitrogen from all three supplied sources.
研究了豌豆（Pisum sativum L.）叶片在先前用（15）N 标记后，短期（2 小时）内从硝酸盐、谷氨酰胺或天冬酰胺中掺入氮的情况，这些氮源被作为未标记的（14）N 示踪剂供应。然后，追踪组织中各种氨基酸成分中（15）N 的消除情况。大多数成分都有活性和非活性池。硝酸盐产生的氨通过谷氨酰胺的酰胺基团被同化。当供应谷氨酰胺时，其氮迅速转移到谷氨酸、天冬酰胺和其他产物中，并有一些转移到氨中。天冬酰胺中的氮广泛分布到氨和氨基酸化合物中。有一个快速的直接向谷氨酰胺的转移，这似乎不涉及游离氨。丙氨酸氮可以直接从天冬酰胺中获得，可能是通过转氨基作用。大量的同型丝氨酸可以从三种氮源中合成。同型丝氨酸似乎比游离天冬氨酸更容易从天冬酰胺中获得氮。大量的γ-氨基丁酸池被周转，并从所有三种供应的氮源中得到补充。
