The transcription regulator AllR senses both allantoin and glyoxylate and controls a set of genes for degradation and reutilization of purines

Purines are degraded via uric acid to yield allantoin. Under anaerobic conditions, allantoin is further degraded via carbamoylphosphate to NH(4)+ to provide a nitrogen source and, under aerobic conditions, to 3-phosphoglycerate via glyoxylate for energy production. In this study, we found that a DNA-binding transcription factor AllR, together with AllS, plays a key role in switching control of two pathways, nitrogen assimilation and energy production. The repressor function of AllR is activated in the presence of allantoin, the common substrate for both pathways, leading to repression of the genes for energy production. On the other hand, when glyoxylate is accumulated, AllR is inactivated for derepression of the pathway for energy production. RutR, the master regulator for pyrimidines and arginine, is also involved in this pathway-switching control.