[Objective] In order to find a safe and stable method to produce collagenase in vitro,we expressed the Bacillus cereus collagenase colR75E in Pichia pastoris.[Methods] With the Bacillus cereus genomic DNA as template,we successfully amplified the collagenase colR75E DNA fragment by PCR and cloned it into pPICZαA plasmid.The pPICZαA/colR75E recombinant plasmid was lineared with Sac I,and then the lineared plasmid was transformed into Pichia pastoris X-33 competent cell in order to integrate the inducible AOX1 promoter controlled colR75E fragment into Pichia pastoris X-33 genomic DNA.The successfully integrated Pichia pastoris X-33 strains was cultured and induced by methanol addition.To acquire the highest production,the optimized conditions for ColR75E collagenase expression in Pichia pastoris X-33 were investigated here.After induction,we purified recombinant ColR75E collagenase in supernatant sequentially by ammonium sulfate precipitation,desalting and affinity capture.Finally,the recombinant collagenase ColR75E was analyzed by catalytic activity assay,SDS-PAGE,zymography,type Ⅰ collagen proteolysis and substrate specificity assay.[Results] The highest level of collagenase ColR75E induction was gained under pH 6.0 for 72 hours incubation by 2.5% methanol.As expected,the molecular weight of the recombinant collagenase is nearly 110 kD to ColR75E.The results of zymography and type Ⅰ collagen degradation analysis uncovered that the recombinant collagenase ColR75E had an excellent collagen proteolysis activity.Its specific activity after purification reached to nearly 4.977 U/mg under standard conditions.The recombinant collagenase ColR75E exhibited specific proteolysis to type Ⅰ collagen,but not to BSA,Casein or Lysozyme.[Conclusion] Pichia eukaryotic expression system is suitable for the expression of Bacillus cereus collagenase ColR75E,which supplied a good basement both for its subsequent theoretic research and industrial exploitation.%[目的]利用毕赤酵母真核表达系统表达蜡样芽孢杆菌胶原酶ColR75E,寻找一种安全、稳定的方式体外制备具有高活性的胶原酶.[方法]以蜡样芽孢杆菌R75E基因组DNA为模板,采用PCR法扩增胶原酶colR75E基因,构建pPICZαA/colR75E重组质粒,将该质粒线性化后电转化至毕赤酵母X-33菌株,诱导其表达并对表达条件进行优化.将表达后的酵母发酵液上清通过硫酸铵沉淀、脱盐处理及亲和层析纯化步骤获得高纯度重组ColR75E胶原酶.利用胶原酶活力测定、SDS-PAGE电泳、胶原酶谱、Ⅰ型胶原蛋白及不同底物蛋白降解产物电泳等方法对重组胶原酶ColR75E的活性及底物特异性进行分析.[结果]毕赤酵母中最佳表达重组胶原酶ColR75E的条件为pH 6.0,甲醇终浓度为2.5%,诱导时间72 h,诱导后的蛋白经SDS-PAGE、胶原酶谱以及l型胶原蛋白降解产物电泳分析发现,毕赤酵母中表达的重组胶原酶分子量符合预期,蛋白纯度超过95%,具有较好的胶原蛋白水解活性并测得其比活力为4.977 U/mg.该酶对Ⅰ型胶原蛋白表现出较好的专一性,但是对牛血清白蛋白、酪蛋白及溶菌酶蛋白没有水解活性.[结论]利用毕赤酵母真核表达系统能够获得高活性的蜡样芽孢杆菌胶原酶ColR75E,为该胶原酶广泛应用于医疗、食品等工业领域奠定了理论和方法基础.
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