Sucrose-cleaving enzyme that provides UDP-glucose and fructose for various metabolic pathways. Modulates metabolic homeostasis and direct carbon towards starch synthesis in developing seeds. an NDP-alpha-D-glucose + D-fructose = a ribonucleoside 5'-diphosphate + H(+) + sucrose Optimum pH is 6.0-7.0 for degradative reaction (PubMed:22184213, PubMed:17257168). Optimum pH is 7.0 for synthetic reaction (PubMed:22184213). Optimum pH is 9.0-9.5 for synthetic reaction (PubMed:17257168). Detected in the whole plant with highest expression in developing siliques, vasculature of cotyledons and stomatal guard cells. Also detected throughout the mature parts of the root but not in the expanding zone. Highly expressed in late-maturing seeds and in geminating seeds (at the protein level). By drought stress. By mannitol, an osmotic agent. Positively regulated by LEC2. No visible phenotype. Diminution of the starch content of developing seeds and increased lipid accumulation early during seed development. Belongs to the glycosyltransferase 1 family. Plant sucrose synthase subfamily.