The use of oxidoreductases as biocatalysts for industrial production of valuable compounds has a strong demand for NADP. Herein, we prepared superparamagnetic NAD kinase catalyst to synthesize NADP in vitro. First, Fe3O4 particles were synthesized through a solvothermal method, followed by the chemical modification with epichloro-hydrin, iminodiacetic acid, and Ni2+ to yield functional Fe3O4 sub-microspheres. Subsequently, NAD kinase of Escherichia coli was overexpressed and immobilized on to the surface of magnetic sub-microspheres. The immobilized NAD kinase was used to catalyze the conversion of NAD to NADP in a cell-free system. Under optimal condition, the conversion ratio of NAD reached 91.7% and remained at 86.3% after repeated use for five times. Our study revealed that the novel magnetic NAD kinase catalyst possessed favorable properties for magnetic manipulation and NADP production.

中文翻译：

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Fe3O4-IDA-Ni/NAD激酶磁性催化剂的制备及酶活性

使用氧化还原酶作为生物催化剂来工业生产有价值的化合物对 NADP 有着强烈的需求。在此，我们制备了超顺磁性 NAD 激酶催化剂以在体外合成 NADP。首先，通过溶剂热法合成 Fe3O4 颗粒，然后用环氧氯丙烷、亚氨基二乙酸和 Ni2+ 进行化学改性，得到功能性 Fe3O4 亚微球。随后，大肠杆菌的 NAD 激酶过表达并固定在磁性亚微球表面。固定化的 NAD 激酶用于在无细胞系统中催化 NAD 向 NADP 的转化。在最佳条件下，NAD的转化率达到91.7%，重复使用5次后仍保持在86.3%。