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 Highly active without 3'phosphoglycerate, and is only slightly affected by the activator 3'phosphoglycerate and inhibitor orthophosphate. Glycan biosynthesis; starch biosynthesis. Heterotetramer. Found in the chloroplast in leaf. Found in the plastid in the developing endosperm. Leaves. Belongs to the bacterial/plant glucose-1-phosphate adenylyltransferase family.