Common Degradative Pathways of Morpholine, Thiomorpholine, and Piperidine by Mycobacterium aurum MO1: Evidence from (1)H-Nuclear Magnetic Resonance and Ionspray Mass Spectrometry Performed Directly on the Incubation Medium

In order to see if the biodegradative pathways for morpholine and thiomorpholine during degradation by Mycobacterium aurum MO1 could be generalized to other heterocyclic compounds, the degradation of piperidine by this strain was investigated by performing (1)H-nuclear magnetic resonance directly with the incubation medium. Ionspray mass spectrometry, performed without purification of the samples, was also used to confirm the structure of some metabolites during morpholine and thiomorpholine degradation. The results obtained with these two techniques suggested a general pathway for degradation of nitrogen heterocyclic compounds by M. aurum MO1. The first step of the degradative pathway is cleavage of the C—N bond; this leads formation of an intermediary amino acid, which is followed by deamination and oxidation of this amino acid into a diacid. Except in the case of thiodiglycolate obtained from thiomorpholine degradation, the dicarboxylates are completely mineralized by the bacterial cells. A comparison with previously published data showed that this pathway could be a general pathway for degradation by other strains of members of the genus Mycobacterium.

为探究金色分枝杆菌MO1（Mycobacterium aurum MO1）降解吗啉（morpholine）与硫代吗啉（thiomorpholine）的生物降解途径能否推广至其他杂环化合物（heterocyclic compounds），本研究通过直接对孵育培养基进行(1)H-核磁共振（(1)H-nuclear magnetic resonance）检测，分析了该菌株对哌啶（piperidine）的降解情况。此外，本研究在未对样品进行纯化的前提下采用离子喷雾质谱（Ionspray mass spectrometry）进行检测，以确证吗啉与硫代吗啉降解过程中部分代谢产物的结构。通过上述两种技术获得的结果表明，金色分枝杆菌MO1降解含氮杂环化合物存在一条通用途径。该降解途径的第一步为C—N键断裂，由此生成一种中间氨基酸；随后该氨基酸经脱氨作用并被氧化为二羧酸。除硫代吗啉降解产生的硫代二羟乙酸盐外，其余二羧酸盐均可被该细菌细胞完全矿化。通过与已发表的相关数据进行比对，本研究发现该降解途径或许可推广至分枝杆菌属（Mycobacterium）其他菌株的降解过程。