D-glucose 6-phosphate + UDP-alpha-D-glucose = alpha,alpha-trehalose 6-phosphate + H(+) + UDP Binds to the phosphopeptide-binding site of GRF/14-3-3 and to MBF1c. Low expression in leaves, stems, flower buds, flowers and siliques. 90-fold induction by sucrose after 24 hours and by heat stress. Both Ser-5 and Thr-32 must be phosphorylated for binding to GRF/14-3-3. 2-deoxyglucose, but not phenformin, enhances the phosphorylation of TPS5. In the N-terminal section; belongs to the glycosyltransferase 20 family. In the C-terminal section; belongs to the trehalose phosphatase family.