The IEF PAGE showed that the wild type and M222A mutant had the same pI of 8.92,while those of double mutant,triple mutant and tetra mutant were 8.88,9.10 and 9.17 respectively.

• 野生型碱性蛋白酶与（M222A）突变种的等电点均为8?92，而（M222A，N118S），（M222A，N118S，Q103R）和（M222A，N118S，Q103R，D60N）突变酶分别为8?88，9?10和9?17。