Involved in synthesis of starch. Catalyzes the synthesis of ADP-glucose, a molecule that serves as an activated glycosyl donor for alpha-1,4-glucan synthesis. Essential for starch synthesis in leaf chloroplasts. alpha-D-glucose 1-phosphate + ATP + H(+) = ADP-alpha-D-glucose + diphosphate Activated by 3'phosphoglycerate, inhibited by orthophosphate. Allosteric regulation. Glycan biosynthesis; starch biosynthesis. Heterotetramer composed of two small and two large subunits. Expressed in stems. Expressed in developing seeds from 4 to 12 days after flowering (DAF). Induced by sucrose, glucose and abscisic acid (ABA). Belongs to the bacterial/plant glucose-1-phosphate adenylyltransferase family.