【摘要】 本文报道用含ｔｙｒＢ基因（在大肠杆菌中编码芳香族氨基酸转氨酶）的质粒ｐＫＢ７转化不同的突主菌，筛选出ＣＴＢ２菌（ｐＫＢ７转化ＪＭ１０７得到）表达的芳香族氨基酸转氨酶活力最高。进一步研究证明ＣＴＢ２菌在菌浓度为２０ｍｇ／ｍｌ，温度３０℃，反就６０分钟．能催化苯丙酮酸加氨生成大量的Ｌ－苯内氮酸，而没有付产物酪氨酸生戊。以从ＣＴＢ２菌中提取纯化出的质粒为模板，经ＰＣＲ扩增反应可以得到约长１．２ｋｂ的ｔｙｒＢ基因片段，ＳＤＳ－聚丙烯酰胺凝胶电泳实验表明ＣＴＢ２菌可溶性蛋白在分子量约４００００，有一条明显加深的蛋白区带，这与理论估算的芳香族氨基酸转氨酶的分子量４３０００基本一致。而ＪＭ１０７和含ｐＫＫ２３３－２空质粒的ＪＭ１０７在该位点的区带则没有加深，该加深区带的蛋白含量占到总溶性蛋白的２０％左右。更多还原

【Abstract】 he recombinant plasmid pKB7 contains E. coli tyrB gene which codes for aromatic transaminase.Atransformant,JM107 with pKB7,was selected from different transformants with pKB7.This strain isnamed CTB2.After CTB2 mixed with phenylpyruvic acid and L-aspartic acid at the optimum cell con-centration 20 mg/ml,and at 30℃ for about 60 mintites,a large amount of L-phenylalanine withoutby-product tyrosine was observed.After reutilizing CTB2 for seven times,we found that there stillwas 50%of the transaminase activitv remained;Restilts showed that there were no remarkably differ-ences between the phenylpyruvic acids made in China and by Sigma Corp.for CTB2.While the plas-mid extracted from CTB2 was used as DNA template,a 1.2Kb tyrB fragment could be observed byPCR. SDS-PAGE demonstrated that the band at 40,000 dalton of CTB2 is darker than the same bandsof JM107 and CTB9(Jm107 with pKK23-2).The molecular weight of this darker band consistswith the theoretical molecular weight of E,coli aromatic transaminase;The amount of protein in thisdarker band is about 20%of the total dissoluble proteins.更多还原