Safety assessment of genetically engineered yeast and breeding of non-toxigenic industrially used yeasts

通过测定甲基乙二醛(MG)细胞水平的变化来评估基因工程酵母细胞的安全性。甲基乙醛(MG)是一种典型的毒性酮醛，由二羟丙酮磷酸在甲基乙醛合成酶(MGS)的作用下合成。得到了以下结果。(1)转化糖酵解酶基因(磷酸葡萄糖异构酶基因、磷酸果糖激酶基因和丙糖磷酸异构酶基因)的酿酒酵母细胞在大量葡萄糖的发酵条件下，MG在细胞内的积累达到诱变水平。(2)酶学研究表明MGS对观察到的MG的积累负有全部责任。(3)MGS的缺乏显著降低了细胞内的MG水平。根据这些结果，检测基因工程酵母细胞中MG的波动对于在实际发酵过程中安全利用所产生的酵母是必要的。此外，还在REL…中研究了MG的生理功能酵母菌产孢量较大。该酶的活性与清酒酵母的产孢量密切相关。这一发现被应用于没有产孢力的清酒酵母细胞。MG的去除显著提高了清酒酵母的产孢率，为杂交分子育种提供了手段。1995年荣获日本发酵与生物工程学会“EDA奖”。安全性评价扩展到大豆球蛋白基因转基因马铃薯。大豆球蛋白的表达水平约为马铃薯总蛋白的1%。脂肪、碳水化合物、灰分、纤维、维生素和脂肪酸水平与对照(转基因马铃薯或未转基因的天然马铃薯)几乎相同。而含有赤霉素基因载体或载体的转基因马铃薯，其糖类生物碱(茄素和茶黄素)的含量增加，达到对照的1.5-2倍。结果表明，载体与待转化植物的适当组合对于创造转基因植物和/或转基因食品具有重要意义。较少

The safety of genetically engineered yeast cells was assessed by determining the change in cellular level of methylglyoxal (MG), a typical toxic ketoaldehyde biosynthesized from dihydroxyacetonephosphate by an action of methylglyoxal synthase (MGS). The following results were obtained. (1) when the cells of Saccharomyces cerevisiae transformed with glycolytic enzyme genes (phosphoglucose isomerase, phosphofructokinase and triosephosphate isomerase genes) were incubated in fermentation conditions with large amount of glucose, MG was accumulated in cells at a mutagenic level. (2) The enzymatic study indicated that MGS was entirely responsiblefor the observed accumulation of MG.(3) The deficiency of MGS dramatically lowered the cellular MG level. From these results, the inspection of MG fluctuation in genetically engineered yeast cells is necessary for the safety utilization of the created yeast in practical fermenta-tion processes.The physiological function of MGS was also studied in rel … More ation to the yeast sporulation. The activity of the enzyme was closely related to the sporulation capability of Sake yeasts. The finding was applied to the Sake yeast cells that show no sporulation capability. The removal of MG resulted in the marked increase in sporulation efficiency of Sake yeast and provided means for molecular breeding by hybridization. We were awarded a "Eda prize" from Japan Society of Fermentation and Bioengineering in 1995.The safety assessment was extended to the genetically transformed potato with soybean glycinin gene. The expression level of glycinin was about 1% of the total potato protein. The levels of lipid, carbohydrate, ash, fiber, vitamin, and fatty acids were almost the same as those of control (transformed potato with a vector or non-transformed natural potato). However, transformed potato with a vector or the vector habouring giycinin gene showed increased level of glycoalkaroids (solanin and chakonin) and the level reached 1.5-2 fold of the control. The results indicated that the suitable combination of vector and plant to be transformed is important in creation transgenic plant and/or genetically engineered foods. Less