Pierwola Agnes, Krupinski Tomasz, Zalupski Peter, Chiarelli Michael, Castignetti Domenic
Department of Biology, Loyola University of Chicago, Chicago, Illinois 60626, USA.
Appl Environ Microbiol. 2004 Feb;70(2):831-6. doi: 10.1128/AEM.70.2.831-836.2004.
Siderophores are avid ferric ion-chelating molecules that sequester the metal for microbes. Microbes elicit siderophores in numerous and different environments, but the means by which these molecules reenter the carbon and nitrogen cycles is poorly understood. The metabolism of the trihydroxamic acid siderophore deferrioxamine B by a Mesorhizobium loti isolated from soil was investigated. Specifically, the pathway by which the compound is cleaved into its constituent monohydroxamates was examined. High-performance liquid chromatography and mass-spectroscopy analyses demonstrated that M. loti enzyme preparations degraded deferrioxamine B, yielding a mass-to-charge (m/z) 361 dihydroxamic acid intermediate and an m/z 219 monohydroxamate. The dihydroxamic acid was further degraded to yield a second molecule of the m/z 219 monohydroxamate as well as an m/z 161 monohydroxamate. These studies indicate that the dissimilation of deferrioxamine B by M. loti proceeds by a specific, achiral degradation and likely represents the reversal by which hydroxamate siderophores are thought to be synthesized.
铁载体是一类能与铁离子紧密螯合的分子，可为微生物螯合金属。微生物在众多不同环境中都会产生铁载体，但这些分子重新进入碳和氮循环的方式却鲜为人知。本研究调查了从土壤中分离出的中慢生根瘤菌对三羟基肟酸铁载体去铁胺B的代谢情况。具体而言，研究了该化合物裂解为其组成单羟基肟酸的途径。高效液相色谱和质谱分析表明，中慢生根瘤菌的酶制剂可降解去铁胺B，产生质荷比（m/z）为361的二羟基肟酸中间体和质荷比为219的单羟基肟酸。二羟基肟酸进一步降解，产生第二个质荷比为219的单羟基肟酸分子以及质荷比为161的单羟基肟酸。这些研究表明，中慢生根瘤菌对去铁胺B的异化作用通过特定的非手性降解进行，可能代表了羟基肟酸铁载体被认为的合成逆转过程。
