InterPro: IPR000583 Glutamine amidotransferase, class-II

A large group of biosynthetic enzymes are able to catalyse the removal of the ammonia group from glutamine and then to transfer this group to a substrate to form a new carbon-nitrogen group. This catalytic activity is known as glutamine amidotransferase (GATase) (EC:2.4.2) [1]. The GATase domain exists either as a separate polypeptidic subunit or as part of a larger polypeptide fused in different ways to a synthase domain. On the basis of sequence similarities two classes of GATase domains have been identified [2, 3], class-I (also known as trpG-type) and class-II (also known as purF-type). Enzymes containing Class-II GATase domains include amido phosphoribosyltransferase (glutamine phosphoribosylpyrophosphate amidotransferase) (EC:2.4.2.14), which catalyses the first step in purine biosynthesis (gene purF in bacteria, ADE4 in yeast); glucosamine--fructose-6-phosphate aminotransferase (EC:2.6.1.16), which catalyses the formation of glucosamine 6-phosphate from fructose 6-phosphate and glutamine (gene glmS in Escherichia coli, nodM in Rhizobium, GFA1 in yeast); and asparagine synthetase (glutamine-hydrolizing) (EC:6.3.5.4), which is responsible for the synthesis of asparagine from aspartate and glutamine. A cysteine is present at the N-terminal extremity of the mature form of all these enzymes.

This domain is found in a number of cysteine peptidases belonging to MEROPS peptidase family C44 and their non-peptidase homologs.