Histamine (HIS) degradation in microorganisms: imidazole ring splitting and formation of imidazolyl ethanol (IMET) and imidazolyl acetic acid (IMAC) in mycobacteria.

Mycobacterium smegmatis SN 46, isolated from a fatal human oesophagus infection, is able to degrade HIS by imidazole ring splitting. In this respect, SN 46 is unique under the bacteria strains tested. Some other mycobacteria (M. diernhoferi, M. fortuitum, M. chelonei etc.) oxidize HIS to IMET and IMAC without further change. Cell-free extracts of SN 46 transform HIS to IMET and IMAC, while ring splitting enzymes are not detectable. IMAC and IMET were identified by combined gas-liquid chromatography and mass-spectrometry. At present, the possibility of HIS degradation by SN 46 via imidazolyl acetaldehyde (according to the pathway in vertebrates) can not be excluded.