This protein plays a role in synthesis of starch. It catalyzes the synthesis of the activated glycosyl donor, ADP-glucose from Glc-1-P and ATP. 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. Found in the chloroplast in leaf. Found in the plastid in developing endosperm. Abundant in the embryo and is also present in the endosperm. Belongs to the bacterial/plant glucose-1-phosphate adenylyltransferase family.