Fig 1.
Pathways and genes of putrescine catabolism. The transaminase pathway is reactions 2 to 5 (PatA, PatD, GabT, and GabD), and the glutamylated putrescine (GP) pathway is reactions 6 to 9, 4, and 5 (PuuA, PuuB, PuuC, PuuD, PuuE, and PuuC). Reactions 2, 4, and 7 generate ammonia for assimilation. The abbreviations are GLT for glutamate and α-KG for α-ketoglutarate. All the genes considered in this work are indicated in the bottom half, except for patA (b3073). The solid arrows indicate the genes and the direction of transcription, drawn to scale. There are documented promoters preceding puuA, puuD, ydcS, csiD, and gabD. Other promoters may exist. Evidence for a puuAP operon is presented in this work. Evidence for a nitrogen-regulated gabDTPC operon has been presented (46). Evidence for the larger csiD-lhgO-gabDTPC operon controlled by σS has been described (30). The patA gene (not shown) is monocistronic.