Asparaginase is an enzyme that has been purified from E. coli and Erwinia carotovora. It acts by deaminating extracellular L-asparagine, an amino acid that appears to be essential for protein synthesis by some tumour cells lacking adequate levels of asparagine synthetase.

Asparaginase from Erwinia carotovora is serologically and biochemically distinct from asparaginase from E. coli, although its antineoplastic activity and toxicity is similar. Asparaginase is usually considered to be cell cycle phase-nonspecific, but it may block some cells in G1 or S phase.