12月22日，国际著名杂志Nature刊登了国外研究人员的最新研究成果“Intermediates in the transformation of phosphonates to phosphate by bacteria。”研究人员在文章中揭示了细菌利用膦酸酯的方式。
作为核酸、碳水化合物和磷脂的一个成分，磷是所有生命形式所必需的。人们知道，很多细菌在没有磷酸盐时能够将膦酸酯作为磷的一个来源，但人们对其中所涉及的通道仍不是很清楚。本文作者们探讨了大肠杆菌在phn基因簇的引导下将膦酸烷基酯转化成磷酸盐的机制。在phn操纵子内的14个基因当中，7个以前曾被发现是膦酸酯利用所必需的，但对其中任何一种蛋白都未发现催化功能。现在，这个反应序列已被确定。在该过程的最后一步，关键碳-磷键在一个基于自由基的反应中被断开，而这个反应的进行则依赖于S-adenosyl- L-methionine辅因子的存在。（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.
