Formation of N-ethylmaleimide (NEM)-glutathione conjugate and N-ethylmaleamic acid revealed by mass spectral characterization of intracellular and extracellular microbial metabolites of NEM

The extracellular and intracellular metabolites formed upon exposure of activated sludge microorganisms to a sublethal concentration of N-ethylmaleimide were monitored by liquid chromatography with ion trap mass spectrometry. The metabolite N-ethylsuccinimido-S-glutathione (m/z 433) was converted rapidly to N-(2-oxoethyl)-2,2-(propionylamino)propanamide (m/z 187) and N-ethylmaleamic acid (m/z 144).