Bochner B R, Savageau M A
Mol Gen Genet. 1979 Jan 5;168(1):87-95. doi: 10.1007/BF00267937.
Imidazole propionic acid (ipa), a gratuitous inducer of the histidine-utilization (hut) system in Salmonella typhimurium, inhibits the organism's growth on succinate minimal medium. Induction of the hut system is necessary, but not sufficient, to cause inhibition. A study of the ability of single amino acids to relieve ipa-restricted growth suggests that insufficient glutamate is the cause of slow growth. The inhibition of growth by imidazolone propionic acid (iopa), an intermediate in the catabolism of histidine to glutamate, is similar to that by ipa. Studies using 2, 3, 5-triphenyl tetrazolium chloride plates to examine amino acid catabolism suggest that accumulation of ipa or iopa leads to inactivation of aspartate amino-transferase (AAT). This interpretation is supported by studies of an Escherichia coli mutant lacking AAT. The mutant grows poorly on succinate minimal medium, and the poor growth is relieved by the same amino acids that relieve ipa- and iopa-restricted growth. These and other findings are discussed in terms of coordination of the histidine-utilization system with enzymatic activities involved in the catabolism of other amino acids.
咪唑丙酸（ipa）是鼠伤寒沙门氏菌中组氨酸利用（hut）系统的一种 gratuitous 诱导剂，它会抑制该生物体在琥珀酸盐基本培养基上的生长。hut 系统的诱导对于产生抑制作用是必要的，但并不充分。一项关于单个氨基酸缓解 ipa 限制生长能力的研究表明，谷氨酸不足是生长缓慢的原因。咪唑啉酮丙酸（iopa）是组氨酸分解代谢为谷氨酸过程中的一种中间产物，它对生长的抑制作用与 ipa 相似。使用 2,3,5 - 三苯基氯化四氮唑平板检测氨基酸分解代谢的研究表明，ipa 或 iopa 的积累会导致天冬氨酸氨基转移酶（AAT）失活。缺乏 AAT 的大肠杆菌突变体的研究支持了这一解释。该突变体在琥珀酸盐基本培养基上生长不良，而缓解 ipa 和 iopa 限制生长的相同氨基酸可以缓解其生长不良。这些以及其他发现将根据组氨酸利用系统与其他氨基酸分解代谢中涉及的酶活性的协调作用进行讨论。
