Alpha,alpha-trehalose synthase (, trehalose synthase, trehalose synthetase, UDP-glucose:glucose 1-glucosyltransferase, TreT, PhGT) is an enzyme with systematic name ADP-glucose:D-glucose 1-alpha-D-glucosyltransferase. This enzyme catalyses the following chemical reaction
This enzyme requires Mg<sup>2+</sup> for maximal activity.