| Type: | Family | Name: | Bifunctional uridylyltransferase/uridylyl-removing enzyme |
| Description: | This entry describes GlnD, the uridylyltransferase/uridylyl-removing enzyme for signal-transduction protein PII, and acts as the sensory component of the nitrogen regulation (ntr) system [, ]. The ntr system modulates nitrogen metabolism in response to the prevailing nitrogen source and the requirements of the cell. During nitrogen fixation, ammonia and 2-oxoglutarate can be used to produce glutamate. The activity of the PII protein is stimulated by glutamine and inhibited by 2-oxoglutarate. Under glutamate-limiting conditions, PII is uridylylated by GlnD leading to the activation of glutamate synthetase and to the stimulation of NtrC-dependent promoters. Under high concentrations of fixed nitrogen, PII is de-uridylylated leading to the inactivation of the glutamate synthetase pathway and switching off NtrC-dependent promoters [].Not all homologues of PII share the property of uridylyltransferase modification on the characteristic Tyr residue (see ), but the modification site is preserved in the PII homologue of all species with a member of this family. | Short Name: | UTase/UR |
