The influence of different single-site mutations on the specific
activity was unapparent, but the changes of catalytic efficiency
were remarkable. The catalytic efficiency (kcat/Km) in the mutants
E235V, D253P, and E518I increased from 1473.2 mL/mg s (WT)
to 1876.7, 1706.4, and 2038.2 mL/mg s, respectively (Table 2). As
revealed by the 3D structure of 2WAN, the majority of 13 positive
mutants were located in the A domain (Fig. 3). This result may indicate that the A domain of the GH-13 family was closely related to
the overall protein stability, as proposed by Deng et al.[23] and
Duan et al.