原核表达的重组牛凝乳酶原与重组单峰驼凝乳酶原,包涵体经溶解和复性后,酸化/中和处理获得成熟凝乳酶.酸化/中和处理两种酶原时发现二者的活化速率有明显差别.相同条件下,牛凝乳酶原在2h以内即可完全活化,而单峰驼凝乳酶原需3d以上.将牛凝乳酶propeptide序列部分或全部取代单峰驼凝乳酶原相应序列,并构建到相同原核表达载体进行表达与复性,获得的融合蛋白MUT-1和MUT-2经酸化/中和处理,MUT-1在pH 2.0～8.5范围均不能活化,MUT-2的活化情况与单峰驼凝乳酶原相同.这也暗示酶原的激活不仅涉及propeptide与酶活性部位的静电作用,还可能与凝乳酶的结构或酶活相关.%The recombinant bovine and camel prochymosins were expressed in prokaryotic system.The inclusions were dissolved and renatured,then the mature chymosins were produced by acidification/neutralization treatment.We found that the activation rate of these two recombinant prochymosins had obvious difference.The bovine prochymosins were fully activated within 2 h in pH2.0,and the camel prochymosin need above 3d on the same conditions.The propeptide of the camel prochymosin was whole/or partly replaced with the corresponding sequences of the bovine prochymosin.Two fusion proteins MUT-1 and MUT-2 were obtained after expression and renaturation by the same ways.The fusion protein MUT-1 could not be activated in pH2 ～ 8.5,and the fusion protein MUT-2 had the similar activation rate with the recombinant prochymosin.It suggested that the activation of prochymosin not only involved electrostatic interactions between the propeptide and the enzyme active site,but also related to the structure or enzyme activity of chymosin.
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