THE REGULATION OF NITROGEN-UTILIZATION IN ENTERIC BACTERIA
THE REGULATION OF NITROGEN-UTILIZATION IN ENTERIC BACTERIA
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DOI：
10.1002/jcb.240510108
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发表时间：
1993-01-01
影响因子：
4
通讯作者：
MAGASANIK, B
中科院分区：
文献类型：
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作者：
MAGASANIK, B
长期以来，已知肠细菌在含有葡萄糖作为唯一碳源和氨作为唯一氮源的培养基中快速生长。然而，它们能够利用许多碳化合物代替葡萄糖作为碳和能量的唯一来源，并且利用许多有机和无机氮化合物代替氨作为氮的唯一来源。通常，葡萄糖的存在抑制利用替代能源所需的酶（分解代谢物抑制），氨类似地抑制利用替代氮源所需的酶（氮调节）。在这两种情况下，这些酶的结构基因的表达受到正调控，并且葡萄糖或氨的存在阻止了在相应基因或操纵子的启动子处转录的起始[Magasanik和Neidhardt，19871.为了理解氮调节的生理学，必须认识到85%的细胞氮来自谷氨酸的氨基氮，15%的细胞氮来自谷氨酸的氨基氮。从谷氨酰胺的酰胺态氮，并考虑氨同化的生化机制。在氨过量的情况下生长的细胞通过还原胺化来自主要碳源的或-酮戊二酸来合成谷氨酸，该反应由NADP连接的谷氨酸脱氢酶催化;它们再次使用氨在谷氨酰胺合成酶（GS）催化的反应中将一部分谷氨酸转化为谷氨酰胺，该反应与ATP水解为ADP和Pi偶联。在生长在
It has long been known that enteric bacteria grow rapidly in a medium containing glucose as only source of carbon and ammonia as only source of nitrogen. They are, however, able to utilize many carbon compounds in place of glucose as sole source of carbon and energy and many organic and inorganic nitrogen compounds in place of ammonia as sole source of nitrogen. Generally the presence of glucose represses the enzymes required for the utilization of the alternative energy sources (catabolite repression), and ammonia similarly represses the enzymes required for the utilization of the alternative nitrogen sources (nitrogen regulation). In both instances the expression of the structural genes for these enzymes is positively regulated and the presence of glucose or ammonia prevents the initiation of transcription at the promoters for the respective genes or operons [Magasanik and Neidhardt, 19871.To understand the physiology of nitrogen regulation it is necessary to realize that 85% of the cellular nitrogen is derived from the amino nitrogen of glutamate and 15% from the amide nitrogen of glutamine and to consider the biochemical mechanism of ammonia assimilation. Cells growing with an excess of ammonia synthesize glutamate by the reductive amination of or-ketoglutarate derived from the major source of carbon, a reaction catalyzed by the NADP-linked glutamate dehydrogenase; they use ammonia again to convert a portion of the glutamate to glutamine in a reaction catalyzed by glutamine synthetase (GS) that is coupled to the hydrolysis of ATP to ADP and Pi. In cells growing on