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

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pnc B和nad E,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,pnc B和nad E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。

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.