强化表达SAM合成酶促进SAM在毕赤酵母中累积

S 腺苷甲硫氨酸 (S adenosyl L methionine ,SAM)是生物体硫代谢的重要中间代谢物质 ,在体内起着转甲基、转硫基、转氨丙基的作用 ,具有重要的药用和保健价值。将酿酒酵母来源的SAM合成酶 2基因置于GAP启动子调控下 ,构建胞内组成型表达质粒 ,并电转化至毕赤酵母菌株GS115。经Zeocin抗性和培养筛选到一株高产SAM的重组菌。对重组菌表达工艺的研究表明 ,碳源、氮源、pH和溶解氧对SAM的累积有较大影响。在优化条件下 ,重组细胞培养 3天 ,SAM累积量可达 2 .49g/L。

Enhancement of the Production of SAM by Overexpression of SAM Synthetase in Pichia pastoris

S-Adenosyl-L-methionine (SAM) is an important metabolic intermediate in the metabolic flux of sulphur. SAM is involved in three key metabolic pathways: transmethylation, transsulfuration and polyamine synthesis. As a potential therapeutic agent, SAM is being used as over the counter drug and nutrient supplement. An expression vector, harboring SAM synthetase 2 gene from S.cerevisiae and regulated by the glyceraldehyde-3- phosphate dehydrogenase gene promoter P GAP, was transformed into GS115 strain of P.pastoris. Through zeocin resistance and expression screening, a recombinant strain was obtained that had high SAM yield and the fermentation conditions were optimized. The results showed that carbon source, nitrogen source, pH and dissolved oxygen had significant effects on the accumulation of SAM. The SAM production of the recombinant cells reached 2.49 g/L after fermentation for three days under the optimized conditions. The present studies show that fermentation of recombinant P.pastoris strain, expressing heterologous SAM synthetase gene, may be a promising approach for the production of SAM.