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

Abstract

ADP-Glucose pyrophosphorylase activity has been detected in relatively low amounts in the embryos and endosperms of sh₂ and bt₂ mutant maize seeds. The total enzyme activities in sh₂ and bt₂ 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 sh₂ enzyme was not as great as that observed with the bt₂ 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.