L-Asparaginase acid L- asparagine to L-aspartic and ammonia

 L-Asparaginase catalyzes the hydrolysis of the non-essential amino acid L- asparagine to L-aspartic and ammonia and have been studied (/explored/exploited) extensively due to potential application in the therapy of acute and chronic lymphoblastic leukemia and lymphosarcoma and Hodgkin’s disease and different types of melanomas.(12)

The anti-neoplastic activity (mechanism) results from (is associated with/follows) cellular protein synthesis inhibition due to depletion of the L-asparagine. Contrary to normal cells, leukemic cells lack asparagine synthetase and their survival depends on an exogenous source.(4) This will ensure that only leukemic cells will be affected by the therapy whereas the normal cells remain unaffected.(7)

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For the last half century, this bacteria-derived enzyme has been used in multi-drug (treatment protocols)chemotherapy regimens, dramatically improve survival, particularly of pediatric patients with high-risk features at the time of diagnosis.(as well as) the cure rate for acute lymphoblastic leukemia (ALL) increased from 5% in 1950’s to 90% in the present days.(7,1)

E.coli and many other bacteria produce two L-asparaginases, a high affinity periplasmic enzyme and a low affinity cytoplasmic enzyme.(14) Synthesis of cytoplasmic asparaginase I is constitutive, while expression of periplasmic asparaginase II is activated during anaerobiosis.(21)However, exclusively the type II enzyme has shown substantial anti-neoplastic activity(capability).(14,21)

 Different types of asparaginase are currently available for clinical application; the isoenzyme II from E. coli  (EcAII) and an L-ASNase isolated from Erwinia chrysanthemi  (ErA) are now the most widely(broadly/conventionally/predominantly/regularly) used. Available(current) preparations(prepared/current formulations) used in the United States and Europe include Native Escherichia coli asparaginase (E. coli-asparaginase) and polyethylene glycol-conjugated asparaginase (PEG-asparaginase) are both derived from Escherichia coli, whereas Erwinia asparaginase is derived from Erwinia chrysanthemi.  (4,3)