A Unique Adenosine Diphosphoglucose Pyrophosphorylase Associated with Maize Embryo Tissue

A comparison of heat stabilities and various kinetic properties between the adenosine diphosphoglucose pyrophosphorylases isolated from endosperm and embryo tissues from starchy maize seeds indicates that the adenosine diphosphoglucose pyrophosphorylase associated with the embryo is distinct from the enzyme isolated from the endosperm. The embryo enzyme is more stable to incubation for 5 minutes at 60 C while the endosperm enzyme is labile to this treatment. Both enzymes are activated by glycerate-3-P. The embryo enzyme is more sensitive to inhibition by phosphate than is the endosperm enzyme. Glycerate-3-P, which reverses the inhibition of the endosperm enzyme by phosphate, has little effect on the phosphate inhibition of the embryo enzyme. Other kinetic studies distinguish the two enzymes.