12月22日,，國際著名雜志Nature刊登了國外研究人員的最新研究成果“Intermediates in the transformation of phosphonates to phosphate by bacteria。”研究人員在文章中揭示了細(xì)菌利用膦酸酯的方式,。
作為核酸,、碳水化合物和磷脂的一個成分,，磷是所有生命形式所必需的。人們知道,，很多細(xì)菌在沒有磷酸鹽時能夠?qū)㈧⑺狨プ鳛榱椎囊粋€來源,，但人們對其中所涉及的通道仍不是很清楚。本文作者們探討了大腸桿菌在phn基因簇的引導(dǎo)下將膦酸烷基酯轉(zhuǎn)化成磷酸鹽的機(jī)制,。在phn操縱子內(nèi)的14個基因當(dāng)中,，7個以前曾被發(fā)現(xiàn)是膦酸酯利用所必需的，但對其中任何一種蛋白都未發(fā)現(xiàn)催化功能?，F(xiàn)在,，這個反應(yīng)序列已被確定。在該過程的最后一步,，關(guān)鍵碳-磷鍵在一個基于自由基的反應(yīng)中被斷開,，而這個反應(yīng)的進(jìn)行則依賴于S-adenosyl- L-methionine輔因子的存在。（生物谷Bioon.com）
doi:10.1038/nature10622
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Intermediates in the transformation of phosphonates to phosphate by bacteria
Siddhesh S. Kamat, Howard J. Williams & Frank M. Raushel
Phosphorus is an essential element for all known forms of life. In living systems, phosphorus is an integral component of nucleic acids, carbohydrates and phospholipids, where it is incorporated as a derivative of phosphate. However, most Gram-negative bacteria have the capability to use phosphonates as a nutritional source of phosphorus under conditions of phosphate starvation1. In these organisms, methylphosphonate is converted to phosphate and methane. In a formal sense, this transformation is a hydrolytic cleavage of a carbon–phosphorus (C–P) bond, but a general enzymatic mechanism for the activation and conversion of alkylphosphonates to phosphate and an alkane has not been elucidated despite much effort for more than two decades. The actual mechanism for C–P bond cleavage is likely to be a radical-based transformation2. In Escherichia coli, the catalytic machinery for the C–P lyase reaction has been localized to the phn gene cluster1. This operon consists of the 14 genes phnC, phnD, …, phnP. Genetic and biochemical experiments have demonstrated that the genes phnG, phnH, …, phnM encode proteins that are essential for the conversion of phosphonates to phosphate and that the proteins encoded by the other genes in the operon have auxiliary functions1, 3, 4, 5, 6. There are no functional annotations for any of the seven proteins considered essential for C–P bond cleavage. Here we show that methylphosphonate reacts with MgATP to form α-D-ribose-1-methylphosphonate-5-triphosphate (RPnTP) and adenine. The triphosphate moiety of RPnTP is hydrolysed to pyrophosphate and α-D-ribose-1-methylphosphonate-5-phosphate (PRPn). The C–P bond of PRPn is subsequently cleaved in a radical-based reaction producing α-D-ribose-1,2-cyclic-phosphate-5-phosphate and methane in the presence of S-adenosyl-L-methionine. Substantial quantities of phosphonates are produced worldwide for industrial processes, detergents, herbicides and pharmaceuticals7, 8, 9. Our elucidation of the chemical steps for the biodegradation of alkylphosphonates shows how these compounds can be metabolized and recycled to phosphate.
