InterPro: IPR000991 Glutamine amidotransferase class-I, C-terminal

Glutamine amidotransferase (GATase) (EC:2.4.2) activity involves the removal of the ammonia group from a glutamate molecule and its subsequent transfer to a specific substrate, thus creating a new carbon-nitrogen group on the substrate. This activity is found in a range of biosynthetic enzymes, including glutamine amidotransferase, anthranilate synthase component II, p-aminobenzoate, and glutamine-dependent carbamoyl-transferase (CPSase). Glutamine amidotransferase (GATase) domains can occur either as single polypeptides, as in glutamine amidotransferases, or as domains in a much larger multifunctional synthase protein, such as CPSase. On the basis of sequence similarities two classes of GATase domains have been identified [1, 2], class-I (also known as trpG-type) and class-II (also known as purF-type). Class-I GATase domains are defined by a conserved catalytic triad consisting of cysteine, histidine and glutamate. Class-I GPTase domains have been found in the following enzymes, the second component of anthranilate synthase and 4-amino-4-deoxychorismate (ADC) synthase; CTP synthase; GMP synthase; glutamine-dependent carbamoyl-phosphate synthase; phosphoribosylformylglycinamidine synthase II; and the histidine amidotransferase hisH.

These signatures also detect peptidases belonging to MEROPS peptidase family C26 (gamma-glutamyl hydrolase), and non-peptidase homologs belonging to family C56 (PfpI endopeptidase) both of which are members of clan PC(C). Other members of family C56 are found in IPR002818.