讨论了大肠杆菌 L -天冬酰胺酶发酵液酶活力的影响因素 ,筛选了大肠杆菌产酶的优化条件 .发现了发酵液酶活力的最适 p H随缓冲介质的变化而变化 ;甘氨酸介质中 ,p H 6 .5 0～ 9.5 0均适于酶活测定 ,且 p H 8.0 0时酶活最高 ;硼酸、Tris...讨论了大肠杆菌 L -天冬酰胺酶发酵液酶活力的影响因素 ,筛选了大肠杆菌产酶的优化条件 .发现了发酵液酶活力的最适 p H随缓冲介质的变化而变化 ;甘氨酸介质中 ,p H 6 .5 0～ 9.5 0均适于酶活测定 ,且 p H 8.0 0时酶活最高 ;硼酸、Tris、磷酸介质中 ,在 p H 8.5 0时 ,酶活力依次下降 ;酶反应的适宜温度 4 0～ 5 0℃ .对菌株培养的研究表明 ,葡萄糖对产酶有抑制作用 ,适当提高摇床转速可使发酵液酶活力由原来的 136 U /m L增至 14 5 U /m L .在确定的最优培养条件 37℃ ,p H 7.0 0 ,2 5 0 r/min下 ,产酶稳定期可持续 12 h.展开更多
The colominic acid was covalently coupled to L asparaginase molecule by reductive amination.Depending on the molar ratios of colominic acid asparaginase (30∶1,50∶1 and 100∶1),a modified enzyme molecule contained 4....The colominic acid was covalently coupled to L asparaginase molecule by reductive amination.Depending on the molar ratios of colominic acid asparaginase (30∶1,50∶1 and 100∶1),a modified enzyme molecule contained 4.7,7.2 and 12 colominic acid molecule,they retained 58%,56% and 33.2% of the initial asparaginase activity,respectively.In comparison with the native enzyme,modified enzyme had lower immunogenicity and antigenicity,longer half life time ( in vitro ),more resistance ability to trypsin proteolysis,and similar Km value for L asparagine.展开更多
文摘讨论了大肠杆菌 L -天冬酰胺酶发酵液酶活力的影响因素 ,筛选了大肠杆菌产酶的优化条件 .发现了发酵液酶活力的最适 p H随缓冲介质的变化而变化 ;甘氨酸介质中 ,p H 6 .5 0～ 9.5 0均适于酶活测定 ,且 p H 8.0 0时酶活最高 ;硼酸、Tris、磷酸介质中 ,在 p H 8.5 0时 ,酶活力依次下降 ;酶反应的适宜温度 4 0～ 5 0℃ .对菌株培养的研究表明 ,葡萄糖对产酶有抑制作用 ,适当提高摇床转速可使发酵液酶活力由原来的 136 U /m L增至 14 5 U /m L .在确定的最优培养条件 37℃ ,p H 7.0 0 ,2 5 0 r/min下 ,产酶稳定期可持续 12 h.
文摘The colominic acid was covalently coupled to L asparaginase molecule by reductive amination.Depending on the molar ratios of colominic acid asparaginase (30∶1,50∶1 and 100∶1),a modified enzyme molecule contained 4.7,7.2 and 12 colominic acid molecule,they retained 58%,56% and 33.2% of the initial asparaginase activity,respectively.In comparison with the native enzyme,modified enzyme had lower immunogenicity and antigenicity,longer half life time ( in vitro ),more resistance ability to trypsin proteolysis,and similar Km value for L asparagine.
