利用辅因子工程策略提高酿酒酵母中S-腺苷蛋氨酸的生物合成

Cofactor engineering strategy for enhanced S-adenosylmethionine production in Saccharomyces cerevisiae

摘要:

通过代谢工程策略改造酿酒酵母胞内辅因子的形式和浓度，分析辅因子NADPH对于产物S-腺苷蛋氨酸 (SAM) 合成的作用并总结能量代谢和其他物质代谢的规律，为高产SAM菌株的代谢工程改造提供理论基础。由于酿酒酵母中的NADPH在线粒体和细胞质中的代谢相对独立，因此以酿酒酵母 BY4741单倍体模式菌株为研究对象，研究了不同亚细胞结构内NADPH对于产物合成的影响。通过激光共聚焦显微镜证实了NADH激酶在酿酒酵母线粒体和细胞质中的表达。实验结果表明NADPH的提高有利于酿酒酵母胞内SAM的合成。发酵24 h，菌株NBYSM-1胞内SAM浓度较对照菌提高3.28倍，菌株NBYSM-2胞内SAM浓度提高1.79倍。其中重组菌株NBYSM-1合成SAM的能力和胞内NADPH/NADP+比率均明显高于重组菌株NBYSM-2。因此，NADPH调控策略有望成为提高SAM产量的有力工具并应用于其他辅因子依赖化合物的合成。

Abstract:

In order to study the role of cofactor engineering in enhancing the production of S-adenosylmethionine (SAM), we altered the form and concentration of cofactor in Saccharomyces cerevisiae through gene recombination. Effects of cofactor on product synthesis, carbon and energy metabolism were analyzed aiming to provide a theoretical basis for a successful metabolic engineering of SAM producing strains. Because NADPH metabolism in mitochondrion and cytoplasm of S. cerevisiae is relatively independent, the effect of intracellular NADPH availability on the production of SAM was studied in different compartments of S. cerevisiae BY4741. The expression of NADH kinase in mitochondria (POS5 encoded) and cytoplasm (POS5Δ17 encoded) was separately confirmed using a laser scanning confocal microscope. NADPH regulation strategy enhanced SAM production. Compared with the control strain, the intracellular SAM concentration of strain NBYSM-1 was increased by 3.28 times, and the intracellular SAM concentration of strain NBYSM-2 was increased by 1.79 times at 24 h fermentation. In addition, SAM titer and NADPH/NADP+ ratio in strain NBYSM-1 were significantly higher than that of strain NBYSM-2. Therefore, NADPH regulation strategy will be a valuable tool for SAM production and could further improve the synthesis of a large range of cofactor-driven chemicals.