Type 1 glutamine amidotransferase (GATase1)-like domain found in peptidase E_like proteins
Type 1 glutamine amidotransferase (GATase1)-like domain found in peptidase E_like proteins. This group contains proteins similar to the aspartyl dipeptidases Salmonella typhimurium peptidase E and Xenopus laevis peptidase E and, extracellular cyanophycinases from Pseudomonas anguilliseptica BI (CphE) and Synechocystis sp. PCC 6803 CphB. In bacteria peptidase E is believed to play a role in degrading peptides generated by intracellular protein breakdown or imported into the cell as nutrient sources. Peptidase E uniquely hydrolyses only Asp-X dipeptides (where X is any amino acid), and one tripeptide Asp-Gly-Gly. Cyanophycinases are intracellular exopeptidases which hydrolyze the polymer cyanophycin (multi L-arginyl-poly-L-aspartic acid) to the dipeptide beta-Asp-Arg. Peptidase E and cyanophycinases are thought to have a Ser-His-Glu catalytic triad which differs from the Cys-His-Glu catalytic triad typical of GATase1 domains by having a Ser in place of the reactive Cys at the nucleophile elbow. Xenopus peptidase E is developmentally regulated in response to thyroid hormone and, it is thought to play a role in apoptosis during tail reabsorption.