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 $\text{sh}_{2}$ and $\text{bt}_{2}$ mutant maize seeds. The total enzyme activities in $\text{sh}_{2}$ and $\text{bt}_{2}$ 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 $\text{sh}_{2}$ enzyme was not as great as that observed with the $\text{bt}_{2}$ 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.