WHY DOES ESCHERICHIA-COLI HAVE 2 PRIMARY PATHWAYS FOR SYNTHESIS OF GLUTAMATE
WHY DOES ESCHERICHIA-COLI HAVE 2 PRIMARY PATHWAYS FOR SYNTHESIS OF GLUTAMATE
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DOI：
10.1128/jb.176.15.4664-4668.1994
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发表时间：
1994-08-01
影响因子：
3.2
通讯作者：
HELLING, RB
中科院分区：
文献类型：
--
作者：
HELLING, RB
大肠杆菌有两条合成谷氨酸的主要途径。谷氨酰胺合成酶-谷氨酸合成酶途径在低氨氮浓度下的合成和谷氨酰胺池的调节中是必不可少的，但谷氨酸脱氢酶(GDH)的必要性一直不确定。在营养受限生长过程中野生型和GDH型突变株之间的竞争实验和直接酶测量的结果表明，当细胞能量(和碳)有限但存在过量的氨和磷时，GDH被用于谷氨酸的合成，而当细胞不处于能量限制下时，则使用谷氨酰胺合成酶-谷氨酸合成酶途径。谷氨酸合成的替代路线的使用意味着，在能量有限的情况下，生物合成的能量成本可能比能量无限时要低。
Escherichia coli has two primary pathways for glutamate synthesis. The glutamine synthetase-glutamate synthase pathway is known to be essential for synthesis at low ammonium concentrations and for regulation of the glutamine pool, but the necessity for glutamate dehydrogenase (GDH) has been uncertain. The results of competition experiments between the wild type and a GDH-deficient mutant during nutrient-limited growth and of direct enzyme measurements suggest that GDH is used in glutamate synthesis when the cell is limited for energy (and carbon) but ammonium and phosphate are present in excess, while the glutamine synthetase-glutamate synthase pathway is used when the cell is not under energy limitation. The use of alternative routes for glutamate synthesis implies that the energy cost of biosynthesis may be less when energy is limited than when energy is unlimited.