Sucrose-cleaving enzyme that provides UDP-glucose and fructose for various metabolic pathways. an NDP-alpha-D-glucose + D-fructose = a ribonucleoside 5'-diphosphate + H(+) + sucrose Predominantly expressed in the leaf tissues and in caryopses. In the caryopse, slightly expressed during the middle storage phase and was strongly expressed at the later storage phase. Belongs to the glycosyltransferase 1 family. Plant sucrose synthase subfamily.