Rittmann Doris, Sorger-Herrmann Ulrike, Wendisch Volker F
Institute of Biotechnology 1, Research Center Juelich, D-52425 Juelich, Germany.
Appl Environ Microbiol. 2005 Aug;71(8):4339-44. doi: 10.1128/AEM.71.8.4339-4344.2005.
Phosphorus is an essential component of macromolecules, like DNA, and central metabolic intermediates, such as sugar phosphates, and bacteria possess enzymes and control mechanisms that provide an optimal supply of phosphorus from the environment. UDP-sugar hydrolases and 5' nucleotidases may play roles in signal transduction, as they do in mammals, in nucleotide salvage, as demonstrated for UshA of Escherichia coli, or in phosphorus metabolism. The Corynebacterium glutamicum gene ushA was found to encode a secreted enzyme which is active as a 5' nucleotidase and a UDP-sugar hydrolase. This enzyme was synthesized and secreted into the medium when C. glutamicum was starved for inorganic phosphate. UshA was required for growth of C. glutamicum on AMP and UDP-glucose as sole sources of phosphorus. Thus, in contrast to UshA from E. coli, C. glutamicum UshA is an important component of the phosphate starvation response of this species and is necessary to access nucleotides and related compounds as sources of phosphorus.
磷是大分子（如DNA）以及中心代谢中间体（如磷酸糖）的重要组成部分，细菌拥有酶和调控机制，能从环境中获取最佳的磷供应。UDP - 糖水解酶和5' - 核苷酸酶可能在信号转导中发挥作用，就像它们在哺乳动物中那样，也可能在核苷酸补救过程中发挥作用，如大肠杆菌的UshA所证明的，或者在磷代谢中发挥作用。发现谷氨酸棒杆菌基因ushA编码一种分泌型酶，该酶作为5' - 核苷酸酶和UDP - 糖水解酶具有活性。当谷氨酸棒杆菌缺乏无机磷酸盐时，这种酶会合成并分泌到培养基中。UshA是谷氨酸棒杆菌以AMP和UDP - 葡萄糖作为唯一磷源生长所必需的。因此，与大肠杆菌的UshA不同，谷氨酸棒杆菌的UshA是该物种磷酸盐饥饿反应的重要组成部分，并且对于利用核苷酸及相关化合物作为磷源是必需的。
