Trehalose-6-Phosphate Synthase (TPS, EC 22.214.171.124) is a glycosyltransferase that catalyses the synthesis of alpha,alpha-1,1-trehalose-6-phosphate from glucose-6-phosphate using a UDP-glucose donor. It is a key enzyme in the trehalose synthesis pathway. Trehalose is a nonreducing disaccharide present in a wide variety of organisms and may serve as a source of energy and carbon. It is characterized most notably in insect, plant, and microbial cells. Its production is often associated with a variety of stress conditions, including desiccation, dehydration, heat, cold, and oxidation. This family represents the catalytic domain of the TPS. Some members of this domain family coexist with a C-terminal trehalose phosphatase domain.