通过提高胞内辅酶水平促进L-苯甘氨酸的合成

Improve the Synthesis of L-Phenylglycine by Increasing the Intracellular Coenzyme Level

摘要:

NAD（H）是全细胞转化合成L-苯甘氨酸中必需的辅酶，其在胞内的质量摩尔浓度对L-苯甘氨酸的合成至关重要。作者通过共表达烟酸转磷酸核糖激酶和NAD+合酶的编码基因pncB和nadE，以期提高胞内辅酶水平，从而提高全细胞转化效率。结果表明，pncB和nadE的共表达使胞内NAD（H）含量提高了2.35倍，同时添加20 mg/L的烟酸使胞内NAD+含量进一步提高了2.42倍，最终，全细胞催化活性和转化产量分别提高了94%和36.6%，说明在辅酶依赖型全细胞转化中，胞内辅酶水平的提高可以有效提高转化效率。

Abstract:

Coenzyme NAD（H） is necessary for whole cell synthesis of L-phenylglycine，so intracellular NAD（H） level is critical for L-phenylglycine synthesis. In this study，the co-expression of the genes pncB and nadE encoding of nicotinic acid phosphoribosyltransferase and NAD+ synthase separately was conducted to increase intracellular NAD（H） level so as to accelerate the whole-cell transformation. The results showed that the NAD（H） level in whole cell was increased by 2.35-fold when pncB and nadE were co-expressed，and it was further increased by 2.42-fold with the addition of 20 mg/L nicotinic acid（NA）. Significantly，the whole cell catalytic activity and L- phenylglycine yield were increased by 94% and 36.6%，respectively，indicating that the transformation efficiency can be effectively improved by the increase of intracellular coenzyme levels in the coenzyme- dependent whole cell transformation systems.