Liu H L, Ford C, Reilly P J
Department of Chemical Engineering, Iowa State University, Ames 50011, USA.
Protein Eng. 1999 Feb;12(2):163-72. doi: 10.1093/protein/12.2.163.
Six previously constructed and nine newly constructed Aspergillus awamori glucoamylases with multiple mutations made by combining existing single mutations were tested for their ability to produce glucose from maltodextrins. Multiple mutations have cumulative effects on glucose yield, specific activity and thermostability. No general correlation between glucose yield and thermostability was observed, although mutations that presumably impede unfolding at high temperatures uniformly increase thermostability and generally increase glucose yield. Peak glucose yields decrease with increasing temperature. The best combination of high glucose yield, high specific activity and high thermostability occurs in Asn20-->Cys/Ala27-->Cys/Ser30-->Pro/Gly137-->Ala glucoamylase.
对六个先前构建的和九个新构建的泡盛曲霉糖化酶进行了测试，这些酶通过组合现有的单突变产生了多个突变，以检验它们从麦芽糊精中产生葡萄糖的能力。多个突变对葡萄糖产量、比活性和热稳定性具有累积效应。尽管可能阻碍高温下展开的突变一致地提高了热稳定性并通常增加了葡萄糖产量，但未观察到葡萄糖产量与热稳定性之间的普遍相关性。葡萄糖产量峰值随温度升高而降低。高葡萄糖产量、高比活性和高热稳定性的最佳组合出现在Asn20→Cys/Ala27→Cys/Ser30→Pro/Gly137→Ala糖化酶中。
