文章基本信息

标题：PhnJ – A novel radical SAM enzyme from the C–P lyase complex
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作者：Siddhesh S. Kamat ; Siddhesh S. Kamat ; Frank M. Raushel 等
期刊名称：Perspectives in Science
印刷版ISSN：2213-0209
电子版ISSN：2213-0209
出版年度：2015
卷号：4
页码：32-37
DOI：10.1016/j.pisc.2014.12.006
语种：English
出版社：Elsevier
摘要：AbstractPhnJ from the C–P lyase complex catalyzes the cleavage of the carbon–phosphorus bond in ribose-1-phosphonate-5-phosphate (PRPn) to produce methane and ribose-1,2-cyclic-phosphate-5-phosphate (PRcP). This protein is a novel radical SAM enzyme that uses glycyl and thiyl radicals as reactive intermediates in the proposed reaction mechanism. The overall reaction is initiated with the reductive cleavage of S-adenosylmethionine (SAM) by a reduced [4Fe–4S]1+-cluster to form an Ado-CH2∙ radical intermediate. This intermediate abstracts theproRhydrogen from Gly-32 of PhnJ to form Ado-CH3and a glycyl radical. In the next step, there is hydrogen atom transfer from Cys-272 to the Gly-32 radical to generate a thiyl radical. The thiyl radical attacks the phosphorus center of the substrate, PRPn, to form a transient thiophosphonate radical intermediate. This intermediate collapses via homolytic C–P bond cleavage and hydrogen atom transfer from theproShydrogen of Gly-32 to produce a thiophosphate intermediate, methane, and a radical intermediate at Gly-32. The final product, PRcP, is formed by nucleophilic attack of the C2-hydroxyl on the transient thiophosphate intermediate. This reaction regenerates the free thiol group of Cys-272. After hydrogen atom transfer from Cys-272 to the Gly-32 radical, the entire process is repeated with another substrate molecule without the use of another molecule of SAM or involvement from the [4Fe–4S]-cluster again.
关键词：Radical SAM enzyme;Phosphonate metabolism;C-P bond cleavage;Hydrogen transfer