An enzyme isolated from the bacterium Escherichia coli or the bacterium Erwinia carotovora with antileukemic activity. Asparaginase hydrolyzes L-asparagine to L-aspartic acid and ammonia in leukemic cells, resulting in the depletion of asparagine, inhibition of protein synthesis, cell cycle arrest in the G1 phase, and apoptosis in susceptible leukemic cell populations. Asparagine is critical to protein synthesis in leukemic cells; some leukemic cells cannot synthesize this amino acid de novo due to the absent or deficient expression of the enzyme asparagine synthase. The E. carotovora-derived form of asparaginase is typically reserved for cases of asparaginase hypersensitivity. Check for active clinical trialsusing this agent. or A condition in which there is a loss of blood flow to bone tissue, which causes the bone to die. It is most common in the hips, knees, shoulders, and ankles. It may be caused by long-term use of steroid medicines, alcohol abuse, joint injuries, and certain diseases, such as cancer and arthritis. It may also occur at some point in time after cancer treatment that included methotrexate, bisphosphonates, or corticosteroids. Also called avascular necrosis, ischemic necrosis, and osteonecrosis.