A complex of polyethylene glycol conjugated with L-asparaginase. Asparaginase hydrolyzes L-asparagine to L-aspartic acid and ammonia, thereby depleting these cells of asparagine and blocking protein synthesis and tumor cell proliferation, especially in the G1 phase of the cell cycle. The agent also induces apoptosis in tumor cells. Pegylation decreases the enzyme's antigenicity. Asparagine is critical to protein synthesis in leukemic cells, which cannot synthesize this amino acid due to the absence of the enzyme asparagine synthase. or A drug used to treat acute lymphoblastic leukemia (ALL). It is a form of the drug asparaginase that is linked to a substance called PEG, which makes the drug stay in the body longer. Asparaginase is an enzyme that breaks down the amino acid asparagine and may block the growth of tumor cells that need asparagine to grow. It is a type of protein synthesis inhibitor. Also called Oncaspar and PEG-asparaginase.