Abstract
ADP-glucose is glucose donor for srarch synthesis. We identified and purified the enzyme that hydrolyzes ADP-glucose to AMP and G1P from the shoot tissues of germinating rice seeds. The molecular size of purified enzyme was estimated to be 285 kDa polypeptide composed of 70 kDa subunits. The NPP cDNA clone was isolated by using the amino acid sequence information determined by Edman sequencing and nESI-MS/MS analysis. The substrate specificity and the amino acid sequence of the enzyme revealed that it belongs to a widely distributed group of plant nucleotide pyrophosphatase (NPP; EC 3.6.1.9). Immunocytochemical analysis using electron microscopy with anti-NPP antibodies showed that NPP localizes in chloroplasts and cell wall in green leaves. Furthermore, the transient expression analysis of NPP-GFP fusion protein supported that it was transported to the plastid. These results strong suggested that NPP is involved in the regulation of starch biosynthesis.
