In situ H-1 NMR study of the biodegradation of xenobiotics: Application toheterocyclic compounds

In vivo or in situ nuclear magnetic resonance (NMR) offers a powerful tool to study the degradation of xenobiotics by microorganisms. Most studies rep orted are based on the use of heteronuclei, and experiments with xenobiotic s have been limited because specifically labeled xenobiotics are not commer cially available, with the exception of F-19 and P-31. wn>H-1 NMR is, thus, of great interest in this area. To avoid problems caused by the presence o f water and intrinsic metabolite signals, some studies were performed using a deuterated medium or specific detection of protons linked to the C-13-N- 15 enriched pattern. We report here the application of in situ H-1 NMR, per formed directly on culture media, to study the metabolism of heterocyclic c ompounds, In this review, we show that a common pathway is involved in the biodegradation of morpholine, piperidine, and thiomorpholine by Mycobacteri um aurum MO1 and Mycobacterium sp. RP1. In all cases, the first step is the cleavage of the C-N bond, which results in an amino acid. Thiomorpholine i s first oxidized to sulfoxide before the opening of the ring. The second st ep is the deamination of the intermediate amino acid, which leads to the fo rmation of a diacid. We have shown that the cleavage of the C-N bond and th e oxidation of thiomorpholine are initiated by reactions involving a cytoch rome P450.