Presence of ADP-Glucose Pyrophosphorylase in Shrunken-2 and Brittle-2 Mutants of Maize Endosperm.

ADP-Glucose pyrophosphorylase activity has been detected in relatively low amounts in the embryos and endosperms of sh(2) and bt(2) mutant maize seeds. The total enzyme activities in sh(2) and bt(2) were about 12% and 17% respectively, of that found in starchy maize seeds (Dekalb 805). The ADP-glucose pyrophosphorylases from the starchy and mutant maize seeds were activated by 3-phosphoglycerate. However, the extent of the activation of the sh(2) enzyme was not as great as that observed with the bt(2) and Dekalb 805 enzymes. The low levels of ADP-glucose pyrophosphorylase activity in the maize mutants correlate well with the low levels of starch found in the endosperm of these mutants.