The purification and characterization of ADP-glucose pyrophosphorylase A from developing maize seeds.

ADPglucose pyrophosphorylase A (ATP:alpha-D-glucose-1-phosphate adenylyltransferase, EC 2.7.7.27) from developing maize (Zea mays) endosperm was purified 129 fold to apparent homogeneity. The molecular weight estimated by gel filtration and by polyacrylamide gel electrophoresis was 375 000 and 400 000, respectively. The preparation gave a single protein band after SDS-polyacrylamide gel electrophoresis suggesting a monomer mol. wt. of 96 000. It was concluded that ADPglucose pyrophosphorylase A in maize endosperm is a tetramer of four similar molecular weight subunits. Values for the Km for glucose 1-phosphate and ATP were 3.8 . 10(-5) and 1.8 . 10(-4) M, respectively (using the homogeneous preparation).