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?cl00216: L-asparaginase_like Superfamily
Bacterial L-asparaginases and related enzymes Asparaginases (amidohydrolases, E.C. 3.5.1.1) are dimeric or tetrameric enzymes that catalyze the hydrolysis of asparagine to aspartic acid and ammonia. In bacteria, there are two classes of amidohydrolases, one highly specific for asparagine and localized to the periplasm (type II L-asparaginase), and a second (asparaginase- glutaminase) present in the cytosol (type I L-asparaginase) that hydrolyzes both asparagine and glutamine with similar specificities and has a lower affinity for its substrate. Bacterial L-asparaginases (type II) are potent antileukemic agents and have been used in the treatment of acute lymphoblastic leukemia (ALL). A conserved threonine residue is thought to supply the nucleophile hydroxy-group that attacks the amide bond. Many bacterial L-asparaginases have both L-asparagine and L-glutamine hydrolysis activities, to a different degree, and some of them are annotated as asparaginase/glutaminase. This wider family also includes a subunit of an archaeal Glu-tRNA amidotransferase.
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