Miller E S, Brenchley J E
J Bacteriol. 1984 Jan;157(1):171-8. doi: 10.1128/jb.157.1.171-178.1984.
Glutamic acid is synthesized in enteric bacteria by either glutamate dehydrogenase or by the coupled activities of glutamate synthase and glutamine synthetase. A hybrid plasmid containing a fragment of the Salmonella typhimurium chromosome cloned into pBR328 restores growth of glutamate auxotrophs of S. typhimurium and Escherichia coli strains which have mutations in the genes for glutamate dehydrogenase and glutamate synthase. A 2.2-kilobase pair region was shown by complementation analysis, enzyme activity measurements, and the maxicell protein synthesizing system to carry the entire glutamate dehydrogenase structural gene, gdhA. Glutamate dehydrogenase encoded by gdhA carried on recombinant plasmids was elevated 5- to over 100-fold in S. typhimurium or E. coli cells and was regulated in both organisms. The gdhA promoter was located by recombination studies and by the in vitro fusion to, and activation of, a promoter-deficient galK gene. Additionally, S. typhimurium gdhA DNA was shown to hybridize to single restriction fragments of chromosomes from other enteric bacteria and from Saccharomyces cerevisiae.
谷氨酸在肠道细菌中可通过谷氨酸脱氢酶或通过谷氨酸合酶与谷氨酰胺合成酶的联合作用合成。一个含有克隆到pBR328中的鼠伤寒沙门氏菌染色体片段的杂交质粒，可恢复鼠伤寒沙门氏菌和大肠杆菌谷氨酸营养缺陷型菌株的生长，这些菌株在谷氨酸脱氢酶和谷氨酸合酶基因中存在突变。通过互补分析、酶活性测量和大细胞蛋白质合成系统表明，一个2.2千碱基对的区域携带了整个谷氨酸脱氢酶结构基因gdhA。在重组质粒上携带的由gdhA编码的谷氨酸脱氢酶在鼠伤寒沙门氏菌或大肠杆菌细胞中升高了5至100倍以上，并且在两种生物体中都受到调控。通过重组研究以及与启动子缺陷型galK基因的体外融合和激活来定位gdhA启动子。此外，还表明鼠伤寒沙门氏菌gdhA DNA与其他肠道细菌和酿酒酵母染色体的单个限制性片段杂交。
