L-アスパラギナーゼ

解説EC 3.5.1.1．アスパラギンの酸アミド結合を加水分解し，アスパラギン酸とアンモニアを生成する反応を触媒する酵素．モルモット血清，肝臓，微生物から精製されている．大腸菌より単離されたアスパラギナーゼは分子量13.4×104，4個のサブユニットより構成されている．高い基質特異性を有するが，グルタミンに対し作用するものもある．白血病，リンパ腫に対する抑制作用がある．[CAS 9015-68-3]森北出版「化学辞典（第2版）

説明Using the enzyme asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1), it is possible to significantly reduce the formation of the cooking carcinogen acrylamide during roasting, deep-frying, or baking of foods. The enzyme hydrolyzes free asparagine to aspartic acid, thereby preventing the formation of acrylamide by reaction of asparagine with reducing sugars at elevated temperatures during the Maillard reaction. The mitigation of acrylamide formation is especially important for a number of cereal- and potato-based products, including crackers, crispbread, gingerbread, biscuits, French fries, and potato chips. After asparaginase pretreatment, the acrylamide concentration of certain foods could be reduced by up to 97 % [84, 86]. By means of in vitro directed evolution, the properties of asparaginase were optimized. For example, an Asp133Leu mutation of a wild-type enzyme showed a significantly improved thermal stability. The enzyme’s half-life at 50 C increased from 3 to 160 h, and the half-inactivation temperature of the mutant was 9 C higher.

使用Asparaginase from Escherichia coli has been used: to compare the cytotoxic effect of L-asparaginase purified fromStreptomyces brollosaeNEAE-115as a standard in asparaginase assay to quantify asparaginase activities in various eel tissuesto elicit amino acid deprivation

一般的な説明Asparaginase is available in 10-mL vials for intramuscularand IV use in the treatment of acute lymphocytic leukemia.Tumor cells are unable to synthesize asparagine, and thereforemust utilize what is available in the extracellular environment.The agent acts by hydrolyzing extracellular asparagineto aspartate and ammonia. The tumor cells are then deprivedof a necessary nutrient, and protein synthesis is inhibited leadingto cell death. The agent is specific for the G1 phase of thecell cycle. Resistance occurs because of the development ofthe tumor cells ability to produce asparagine synthetase thatallows them to synthesize the required amino acid. Antibodyproduction directed at asparaginase may be stimulated by theagent as well. The agent remains in the extracellular spaceafter parental administration and is 30% protein bound. Themetabolism of the agent has not been well characterized andthe plasma half-life depends on the formulation of the drug.The E. coli-derived agent has a plasma half-life of 40 to 50hours, whereas polyethylene glycol-asparaginase’s half-life is3 to 5 days. Adverse effects include hypersensitivity reactions,fever, chills, nausea, lethargy, confusion, hallucinations,and possibly coma. Myelosuppression is not generallyseen. An increased risk of bleeding and clotting is seen in halfof the patients taking the agent.