Enzymatic production of cytidine diphosphate choline (CDP-choline) using orotic acid and choline chloride as substrates was investigated using a 200-ml beaker as a reaction vessel. When Corynebacterium ammoniagenes KY13505 cells were used as the enzyme source, UMP was accumulated up to 28.6 g/liter (77.6 mm) from orotic acid after 26 h of reaction. In this reaction, UDP and UTP were also accumulated, but CTP, a direct precursor of CDP-choline, was not accumulated sufficiently. Escherichia coli JF646/pMW6 cells, which overproduce CTP synthetase by selfcloning of the pyrG gene, were used together with cells of KY13505 for the enzymatic reaction using orotic acid as a substrate. CTP was produced at 8.95 g/liter (15.1 mm) after 23 h of this reaction. To produce CDP-choline, two additional enzyme activities were needed. E. coli MM294/pUCK3 and MM294/pCC41 cells, which express a choline kinase from Saccharomyces cerevisiae (CKIase; encoded by the CKI gene) and a cholinephosphate cytidylyltransferase from S. cerevisiae (CCTase; encoded by the CCT gene) respectively, were added to this CTP-producing reaction system. After 23 h of the reaction using orotic acid and choline chloride as substrates, 7.7 g/liter (15.1 mm) of CDP-choline was accumulated without addition of ATP or phosphoribosylpyrophosphate (PRPP). ATP and PRPP required in the CDP-choline forming reaction system are biosynthesized by those cells using glucose as a substrate.
研究人员使用 200 毫升烧杯作为反应容器,以芦荟酸和
氯化胆碱为底物,研究了
胞苷二
磷酸胆碱(CDP-
胆碱)的酶法生产。以
氨化科里奈杆菌 KY13505 细胞为酶源,反应 26 小时后,从芦荟酸中积累的
UMP 达到 28.6 克/升(77.6 毫米)。在该反应中,
UDP 和 UTP 也得到了积累,但 CDP-choline 的直接前体 CTP 没有得到充分积累。通过自克隆 pyrG
基因过量产生 CTP 合成酶的大肠杆菌 JF646/pMW6 细胞与 KY13505 细胞一起用于以芦荟酸为底物的酶促反应。反应 23 小时后,CTP 的产量为 8.95 克/升(15.1 毫米)。要生产 CDP-
胆碱,还需要两种酶活性。大肠杆菌 MM294/pUCK3 和 MM294/pCC41 细胞分别表达来自酿酒酵母的
胆碱激酶(CKI 酶;由 CKI
基因编码)和来自酿酒酵母的
胆碱磷酸胞苷键转移酶(CCT 酶;由 CCT
基因编码),它们被加入到这个 CTP 生产反应系统中。以芦荟酸和
氯化胆碱为底物进行反应 23 小时后,在不添加
ATP 或
磷酸核糖基
焦磷酸盐(PRPP)的情况下,积累了 7.7 克/升(15.1 毫米)的 CDP-
胆碱。CDP-choline 形成反应系统所需的
ATP 和 PRPP 是由使用
葡萄糖作为底物的细胞
生物合成的。