Schneider B L, Kiupakis A K, Reitzer L J
Department of Molecular and Cell Biology, The University of Texas at Dallas, Richardson, Texas 75083-0688, USA.
J Bacteriol. 1998 Aug;180(16):4278-86. doi: 10.1128/JB.180.16.4278-4286.1998.
Arginine catabolism produces ammonia without transferring nitrogen to another compound, yet the only known pathway of arginine catabolism in Escherichia coli (through arginine decarboxylase) does not produce ammonia. Our aims were to find the ammonia-producing pathway of arginine catabolism in E. coli and to examine its function. We showed that the only previously described pathway of arginine catabolism, which does not produce ammonia, accounted for only 3% of the arginine consumed. A search for another arginine catabolic pathway led to discovery of the ammonia-producing arginine succinyltransferase (AST) pathway in E. coli. Nitrogen limitation induced this pathway in both E. coli and Klebsiella aerogenes, but the mechanisms of activation clearly differed in these two organisms. We identified the E. coli gene for succinylornithine aminotransferase, the third enzyme of the AST pathway, which appears to be the first of an astCADBE operon. Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. Disruption of astB eliminated succinylarginine dihydrolase activity and prevented arginine utilization but did not impair ornithine catabolism. Overproduction of AST enzymes resulted in faster growth with arginine and aspartate. We conclude that the AST pathway is necessary for aerobic arginine catabolism in E. coli and that at least one enzyme of this pathway contributes to ornithine catabolism.
精氨酸分解代谢产生氨，但不会将氮转移到另一种化合物上，然而大肠杆菌中已知的唯一精氨酸分解代谢途径（通过精氨酸脱羧酶）并不产生氨。我们的目标是找到大肠杆菌中精氨酸分解代谢产生氨的途径并研究其功能。我们发现，之前描述的唯一不产生氨的精氨酸分解代谢途径仅占消耗的精氨酸的3%。对另一条精氨酸分解代谢途径的探索导致在大肠杆菌中发现了产生氨的精氨酸琥珀酰转移酶（AST）途径。氮限制在大肠杆菌和气杆菌中均诱导了该途径，但这两种生物体中激活机制明显不同。我们鉴定出了AST途径的第三种酶——琥珀酰鸟氨酸转氨酶的大肠杆菌基因，它似乎是astCADBE操纵子的第一个基因。其破坏会阻止精氨酸分解代谢、损害鸟氨酸利用，并影响AST途径所有酶的合成。astB的破坏消除了琥珀酰精氨酸水解酶活性并阻止了精氨酸利用，但不损害鸟氨酸分解代谢。AST酶的过量表达导致在精氨酸和天冬氨酸存在下生长更快。我们得出结论，AST途径对于大肠杆菌中需氧精氨酸分解代谢是必需的，并且该途径的至少一种酶有助于鸟氨酸分解代谢。
