In enzymology, a glucose-1-phosphate adenylyltransferase (EC 2.7.7.27) is an enzyme that catalyzes the chemical reaction

ATP + alpha-D-glucose 1-phosphate ${\displaystyle \rightleftharpoons }$ diphosphate + ADP-glucose

Thus, the two substrates of this enzyme are ATP and alpha-D-glucose 1-phosphate, whereas its two products are diphosphate and ADP-glucose.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ATP:alpha-D-glucose-1-phosphate adenylyltransferase. Other names in common use include ADP glucose pyrophosphorylase, glucose 1-phosphate adenylyltransferase, adenosine diphosphate glucose pyrophosphorylase, adenosine diphosphoglucose pyrophosphorylase, ADP-glucose pyrophosphorylase, ADP-glucose synthase, ADP-glucose synthetase, ADPG pyrophosphorylase, ADP:alpha-D-glucose-1-phosphate adenylyltransferase and AGPase. This enzyme participates in starch and sucrose metabolism.

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1YP2, 1YP3, and 1YP4.