Abstract
We investigate the function of nucleotide pyrophosphatase/phosphodiesterase (NPP) in rice. Six NPP isozyme genes have been found in rice. Previously, we purified and characterized NPP1, 2 and 6. NPP1 and 6 were divided into ADP-glucose hydrolyzing type, while NPP2 was nucleotide hydrolyzing type. All NPP isozymes were conjugated with Con A-recognized N-glycans. Furthermore, the expression and targeting of NPP-GFP fusion genes revealed that more than 70% of NPPs localize within the plastid. In the present study, we used matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) techniques exoglycosidase digestions of plastid localized glycoprotein NPP1,to identify N-glycan structures. N-glycan structures were identified 27 types and contained high mannose-type (14.9%), complex-type (53.8 %), and Pauci-mannose-type N-glycans (31.3%).
The overall results suggested that glycoprotein NPP1 targeting to plastid and biogenesis was involved in the trafficking of glycosylated proteins from the endoplasmic reticulum–Golgi system.
