天冬氨酸酶C端缺失突变酶基因的克隆和表达

利用多聚酶链反应（PCR）技术，从天冬氨酸酶基因的3'-端删除42个碱基，缺失突变基因经克隆、转化和筛选，得到一株有C端缺失14肽的天冬氨酸酶突变体表达的转化子．突变酶纯酶活性为野生型酶的1．21倍．圆二色谱和荧光光谱的研究表明，突变酶的结构比野生型酶松散或更具柔性，天冬氨酸酶C端14肽不是其功能所必需的．

Cloning and Expression of the Aspartase Mutant of Deletion from C-terminal End

42 bases were deleted from 3'-end of aspartase gene by means of PCR. The mutated gene of the enzyme was cloned into pUC19 plasmid and the new plasmid was constructed. A recombinant,which produced the aspartase mutant of deletion 14 peptide from C-terminus, has been obtained in our Laboratory. The activity of aspartase mutant was 1. 21 time as much as that of wild type enzyme. The studies on the CD spectra and fluorescence spectrum of the enzyme indicated that the structure of the aspartase mutant was more relaxed or flexible than that of wild type. The results suggested that 14 peptide of C-terminal end was unessential for full aspartase activity.