Abstract
We characterized nucleotide pyrophosphatase (OsNPP1) that hydrolyzes ADPglucose linked to the starch synthesis. We further succeeded to identify and isolate a novel cDNA clone encoding NPP isoform that has high homology (61%) with OsNPP1. This gene was designated as OsNPP2. We produced the transgenic rice cells transformed with Ubi::OsNPP2 and NPP2 was purified from the OsNPP2 overexpressed cells. The molecular size of purified enzyme was estimated to be approximately 70 kDa, and the binding of NPP2 to ConA-Sepharose column indicated that this enzyme is glycoprotein same as NPP1. The NPP1 enzyme catalyzed the hydrolytic cleavage of various nucleotide-sugar. By contrast, NPP2 did not hydrolyze the nucleotide-sugars although the enzyme was able to react the nucleotide diphosphate, such as ADP and UDP. These results strongly suggested that the physiological function of OsNPP2 is distinguishable from that of OsNPP1. The morphological phenotype of OsNPP2 overexpression rice plant also will be discussed.
