Pyridoxal 5′-phosphate (PLP) is the biologically active form of vitamin B₆, essential for cellular function in all domains of life. In many organisms, such as Salmonella enterica serovar Typhimurium and Escherichia coli, this cofactor can be synthesized de novo or salvaged from B₆ vitamers in the environment. Unexpectedly, S. enterica strains blocked in PLP biosynthesis were able to use exogenous PLP and pyridoxine 5′-phosphate (PNP) as the source of this required cofactor, while E. coli strains of the same genotype could not. Transposon mutagenesis found that phoN was essential for the salvage of PLP and PNP under the conditions tested. phoN encodes a class A nonspecific acid phosphatase (EC 3.1.3.2) that is transcriptionally regulated by the PhoPQ two-component system. The periplasmic location of PhoN was essential for PLP and PNP salvage, and in vitro assays confirmed PhoN has phosphatase activity with PLP and PNP as substrates. The data suggest that PhoN dephosphorylates B₆ vitamers, after which they enter the cytoplasm and are phosphorylated by kinases of the canonical PLP salvage pathway. The connection of phoN with PhoPQ and the broad specificity of the gene product suggest S. enterica is exploiting a moonlighting activity of PhoN for PLP salvage.

中文翻译：

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周质磷酸酶PhoN在肠沙门氏菌B6抢救中的意外作用。

吡rid醛5'-磷酸（PLP）是维生素B ₆的生物活性形式，对生命的所有领域的细胞功能至关重要。在许多生物中，例如肠炎沙门氏菌鼠伤寒沙门氏菌和大肠杆菌，这种辅因子可以从头合成，也可以从环境中的B ₆维他命中挽救。出乎意料的是，在PLP生物合成中受阻的肠炎链球菌菌株能够使用外源PLP和吡pyr醇5'-磷酸（PNP）作为所需辅因子的来源，而同一基因型的大肠杆菌菌株却不能。转座子诱变发现phoN对于在测试条件下抢救PLP和PNP至关重要。phoN编码由PhoPQ两组分系统转录调控的A类非特异性酸性磷酸酶（EC 3.1.3.2）。PhoN的周质定位对于PLP和PNP的抢救至关重要，并且体外测定证实PhoN具有磷酸酶活性，以PLP和PNP为底物。数据表明，PhoN使B ₆维他命去磷酸，然后它们进入细胞质并被规范PLP挽救途径的激酶磷酸化。的连接的phoN与PhoPQ和基因产物的广泛的特异性表明沙门氏菌被利用的PhoN的走穴活动PLP打捞。