Reactions involved in the lower pathway for degradation of 4-nitrotoluene by Mycobacterium strain HL 4-NT-1

In spite of the variety of initial reactions, the aerobic biodegradation of aromatic compounds generally yields dihydroxy intermediates for ring cleav age. Recent investigation of the degradation of nitroaromatic compounds rev ealed that some nitroaromatic compounds are initially converted to 2-aminop henol rather than dihydroxy intermediates by a number of microorganisms, Th e complete pathway for the metabolism of 2-aminophenol during the degradati on of nitrobenzene by Pseudomonas pseudoalcaligenes JS45 has been elucidate d previously. The pathway is parallel to the catechol extradiol ring cleava ge pathway, except that 2-aminophenol is the ring cleavage substrate. Here we report the elucidation of the pathway of 2-amino-1-methylphenol (6-amino -m-cresol) metabolism during the degradation of 4-nitrotoluene by Mycobater ium strain NL 4-NT-1 and the comparison of the substrate specificities of t he relevant enzymes in strains JS45 and HL 4-NT-1. The results indicate tha t the 2-aminophenol ring cleavage pathway in strain JS45 is not unique hut is representative of the pathways of metabolism of other o-aminophenolic co mpounds.