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首页> 外文期刊>Applied Microbiology and Biotechnology >Stabilization of Escherichia coli penicillin G acylase against thermal inactivation by cross-linking with dextran dialdehyde polymers
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Stabilization of Escherichia coli penicillin G acylase against thermal inactivation by cross-linking with dextran dialdehyde polymers

机译：通过与葡聚糖二醛聚合物交联来稳定大肠杆菌青霉素G酰基转移酶防止热灭活

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摘要

The thermostabilization of penicillin G acylase (PGA) obtained from a mutant of Escherichia coli ATCC 11,105 by cross-linking with dextran dialdehyde molecules, at a molecular mass of 11,500, 37,700 and 71,000 Da, was studied. The thermal inactivation mechanisms of the native and modified PGA were both considered to obey first-order inactivation kinetics during prolonged heat treatment, forming fully active but temperature-sensitive transient states. The highest enhancement to the thermostability of PGA was obtained using dextran-71000-dialdehyde modification, as a nearly ninefold increase at temperatures above 50 degrees C. The modification of PGA by dextran-11500-dialdehyde resulted in a considerable reduction of the Vm and Km parameters of the enzyme. However, other dextran dialdehyde derivatives used for modification did not cause a meaningful change in either Vm and Km. Modification by dextran dialdehyde derivatives did not result in significant change to either the optimal temperature or the activation energy of PGA. All modified PGA preparations showed lower inactivation rate constants but higher half-lives for inactivation than those of the native PGA at all temperatures studied. As indicated by the half-life times and Ki values, dextran 71000-dialdehyde was found to be more effective at cross-linking in the thermo-stabilization of PGA than any other agent studied in this work.
机译：研究了通过与葡聚糖二醛分子交联，从大肠杆菌ATCC 11,105的突变体获得的青霉素G酰基转移酶（PGA）的热稳定性，该分子的分子量为11,500、37,700和71,000 Da。天然和修饰的PGA的热失活机理都被认为在长时间的热处理过程中服从一级失活动力学，形成了完全活跃但对温度敏感的瞬态。使用dextran-71000-二醛改性可以使PGA的热稳定性得到最大增强，在高于50摄氏度的温度下，PGA的热稳定性提高了近9倍。dextran-11500-二醛对PGA的改性导致Vm和Km大大降低酶的参数。但是，用于修饰的其他右旋糖酐二醛衍生物在Vm和Km中均未引起有意义的变化。右旋糖酐二醛衍生物的改性不会导致最佳温度或PGA活化能的显着变化。在所有研究温度下，所有改性的PGA制剂均显示出较低的失活速率常数，但其半衰期高于天然PGA。如半衰期和Ki值所示，发现葡聚糖71000-二醛在热稳定PGA中比在本工作中研究的任何其他试剂更有效地交联。

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