大连蛇岛蝮蛇类凝血酶基因在毕赤酵母中的克隆表达及分离纯化

根据同源性分析设计引物,通过RT-PCR方法从大连蛇岛蝮蛇毒腺总RNA中合成扩增出类凝血酶基因,之后将该基因克隆到表达载体pPIC9K中,经电激转化后整合至毕赤酵母细胞基因组中.经筛选得到甲醇快速生长型转化子His+Mut+在500 ml摇瓶中培养,甲醇诱导分泌表达.上清液中重组类凝血酶是通过两步柱层析得到:Q Sepharose FF和Benzamidine-Sepharose 4BCL.与天然蛇毒类凝血酶一致,分泌表达的重组类凝血酶具有较强的酯酶活性,但精氨酸甲酯如TAME的水解活性较弱.此重组类凝血酶在37℃中性溶液中保存过夜将分解成小肽,但在0℃下很稳定.该酶的最适pH为8.0.

Expression, Purification and Partial Characterization of Recombinant Gloshedobin, a Thrombin-like Enzyme from The Venom of Gloydius shedaoensis

The cDNA of gloshedobin was synthesized and amplified by RT-PCR from the total RNA of snake (Gloydius shedaoensis) venom gland. The 711 bp nucleotide sequence, which encodes the mature gloshedobin, was cloned into expression vector pPIC 9K and transferred into yeast Pichia pastoris, strain GS115. Transfermants with phenotype His+Mut+ were selected to study their expression. Recombinant protein was conveniently separated and purified from the supernatant by two chromatographic steps: ion exchange chromatography on Q-Sepharose FF and affinity chromatography on Benzamidine-Sepharose 4BCL. Like intact gloshedobin, the recombinant enzyme exhibited strong esterase activity using tripeptide p-nitroanilide derivatives as substrate, but hydrolyzed N-p-tosyl-L-arginine methyl ester (TAME) very weakly. The recombinant protein displayed extreme instability at 37℃ in neutral buffer but higher stability at 0℃, and also, pH is not a key factor to affect its stability while the optimal pH for its enzymatic activity is pH 8.0.