Enhanced the catalytic efficiency and thermostability of maltooligosyltrehalose synthase from Arthrobacter ramosus by directed evolution

Maltooligosyltrehalose synthase (MTSase) is a key enzyme in the preparation of trehalose. Increasing interest in trehalose requires further improvement in the catalytic performance of MTSase in order to increase trehalose yield, but so far, the reports about modification of MTSase revealed that the trahalose yield was increased only by 1%. In this study, the mutant S44 P of MTSase from Arthrobacter ramosus was obtained by directed evolution and showed a decrease in K-m to 3.5 mM from 6.6 mM of wild-type, and an increase in k(cat) /K-m by 2.2-fold. Thus, S44 P exhibited a trehalose yield of 76.9 %, which was 6.6 % higher than that obtained by wild-type enzyme. This improved trehalose yield is potentially of great importance for the industrial application. Meanwhile, S44 P exhibits increased thermostability compared to wild-type. We solved the structures of both wild-type and mutant enzymes and evaluated differences in their structures to elucidate the changed properties, which provides the insight for future modification of MTSase.