Metabolism of 6-aminonicotinic acid in Escherichia coli

A late-log-phase culture of an Escherichia coli nadB pncA double mutant took up 6-[7-14C]aminonicotinic acid and excreted 6-[14C]aminonicotinamide. This mutant also accumulated intracellularly several radioactive compounds which have been tentatively identified as 6-amino analogs of compounds in the pyridine nucleotide cycle. It is concluded that 6-aminonicotinamide and 6-aminonicotinic acid probably exert at least a portion of their bacteriostatic effects by being metabolized, by the enzymes of the pyridine nucleotide cycle, to 6-aminonicotinamide adenine dinucleotide and 6-aminonicotinamide adenine dinucleotide phosphate. These compounds are not electron acceptors and are known inhibitors of some pyridine nucleotide-linked dehydrogenases.