Asparaginases (amidohydrolases, E.C. 3.5.1.1) are enzymes that catalyze the hydrolysis of asparagine to aspartic acid and ammonia. In bacteria, there are two classes of amidohydrolases. This model represents type I L-asparaginases, which are highly specific for asparagine and localized in the cytosol. Type I L-asparaginase acts as a dimer. 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. One example of an enzyme with no L-glutaminase activity is the type I L-asparaginase from Wolinella succinogenes.
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