Metal–organic frameworks (MOFs) have been recently studied for a variety of applications because of their huge surface area, large porosity, and tunable functionality. In this work, for the first time, the efficient immobilization of l -asparaginase (ASNase, EC 3.5.1.1) by using MOF as a simple and novel support is demonstrated. The functional groups, morphology, chemical composition, and crystal structure of the support and immobilized ASNase were investigated by using different methods, including Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectrometer, and X-ray diffraction. Afterward, the enzymatic activities and thermodynamic parameters of the immobilized l -ASNase (ASNase@ZIF-8) were compared with free one. After enzyme immobilization, the optimum temperature shifted from 50 to 60 °C, while the optimum pH remains unchanged at 9.0. However, the pH and thermal stability of the ASNase@ZIF-8 was significantly improved compared to the free one. The ASNase@ZIF-8 displayed an excellent long-term storage stability, which could protect more than 56% of the initial activity at 25 °C for 4 weeks. Besides, the ASNase@ZIF-8 had high reusability, which showed a high degree of activity (more than 45%) after 10 cycles. K m and V max values were 0.18 mM and 64.5 µmol/min for ASNase@ZIF-8 and those for free ASNase were 0.40 mM and 68.0 µmol/min, respectively. The proposed support based on ZIF-8 was superior in terms of high enzyme loading capacity (82.0%), high enzyme catalytic activity, and easy preparation process. Overall, newly developed support for ASNase may provide a new platform for its biotechnological applications.

中文翻译：

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金属有机框架（MOF）：ASNase 固定化的新型支撑平台

金属有机框架（MOFs）由于其巨大的表面积、大的孔隙率和可调的功能，最近被研究用于各种应用。在这项工作中，首次证明了使用 MOF 作为简单而新颖的支持物对 l-天冬酰胺酶 (ASNase, EC 3.5.1.1) 的有效固定。采用傅里叶变换红外光谱、扫描电子显微镜、能谱仪和 X 射线衍射等不同方法研究了载体和固定化 ASNase 的官能团、形貌、化学组成和晶体结构。然后，将固定化的 l-ASNase (ASNase@ZIF-8) 的酶活性和热力学参数与游离酶进行比较。酶固定后，最适温度从 50°C 移至 60°C，而最佳pH值保持在9.0不变。然而，与游离的 ASNase@ZIF-8 相比，ASNase@ZIF-8 的 pH 值和热稳定性显着提高。ASNase@ZIF-8 表现出优异的长期储存稳定性，在 25°C 下 4 周可保护超过 56% 的初始活性。此外，ASNase@ZIF-8 具有很高的可重用性，在 10 个循环后表现出很高的活性（超过 45%）。ASNase@ZIF-8 的 K m 和 V max 值分别为 0.18 mM 和 64.5 µmol/min，而游离 ASNase 的 K m 和 V max 值分别为 0.40 mM 和 68.0 µmol/min。所提出的基于 ZIF-8 的载体在高酶负载能力 (82.0%)、高酶催化活性和易于制备过程方面具有优越性。总体而言，新开发的对 ASNase 的支持可能为其生物技术应用提供一个新平台。