Paris C G, Magasanik B
J Bacteriol. 1981 Jan;145(1):257-65. doi: 10.1128/jb.145.1.257-265.1981.
Klebsiella aerogenes utilized aromatic amino acids as sole sources of nitrogen but not as sole sources of carbon. K. aerogenes abstracted the alpha-amino group of these compounds by transamination and excreted the arylpyruvate portions into the medium. When tryptophan was utilized as the sole source of nitrogen by K. aerogenes, indolepyruvate was excreted into the medium, where it polymerized non-enzymatically to form a brick red pigment. At least four separate aromatic aminotransferase activities were found in K. aerogenes. One activity (aromatic aminotransferase I) appeared to be solely responsible for the aminotransferase reaction necessary for the growth of K. aerogenes when tryptophan was the source of nitrogen; the loss of this activity by mutation (tut) prevented the growth of cells on media containing this and other aromatic amino acids. None of the other aminotransferase activities in the cells could substitute for aromatic aminotransferase in this regard. Tryptophan-dependent pigment formation in K. aerogenes was positively controlled by the intracellular level of glutamine synthetase. Nevertheless, the aromatic aminotransferase activity in cells varied less than 2-fold in response to 10-fold or greater changes in the levels of glutamine synthetase. Glutamine synthetase affected the ability of the cells to take up tryptophan from the medium.
产气克雷伯菌利用芳香族氨基酸作为唯一的氮源，但不能作为唯一的碳源。产气克雷伯菌通过转氨作用提取这些化合物的α-氨基，并将芳基丙酮酸部分分泌到培养基中。当产气克雷伯菌利用色氨酸作为唯一的氮源时，吲哚丙酮酸被分泌到培养基中，在那里它非酶促聚合形成砖红色色素。在产气克雷伯菌中发现了至少四种不同的芳香族氨基转移酶活性。一种活性（芳香族氨基转移酶I）似乎是产气克雷伯菌以色氨酸为氮源生长时转氨反应的唯一原因；该活性因突变（tut）丧失后，细胞无法在含有这种及其他芳香族氨基酸的培养基上生长。在这方面，细胞中的其他氨基转移酶活性都不能替代芳香族氨基转移酶。产气克雷伯菌中色氨酸依赖性色素形成受谷氨酰胺合成酶细胞内水平的正调控。然而，谷氨酰胺合成酶水平变化10倍或更大时，细胞中的芳香族氨基转移酶活性变化不到2倍。谷氨酰胺合成酶影响细胞从培养基中摄取色氨酸的能力。
