15% SDS-PAGE showing overproduction and enzyme purity of three mutants of Klebsiella sp. 601 MCO. (a) expressed products: M. protein molecular weight marker; lane 1. the pellet of E106F/α351-380M; lane 2. the supernatant of E106F/α351-380M; lane 3. the pellet of α351-380M; lane 4. the supernatant of α351-380M; lane 5. the pellet of E106F; lane 6. the supernatant of E106F. (b) purified proteins: lane 1. α351-380M, lane 2. E106F, and lane 3. the wild type.