Title: Distribution and characterization of isotypes of 49 kDa apyrase from pea Japanese

Authors: Motohito Yoneda, Koichi Shibata, Mahmoud F.M. Moustafa, Shunnosuke Abe, Eric Davies

The 49 kDa apyrase (EC from Alaska pea, which hydrolyzes both NTP and NDP into NMP and inorganic phosphate, was present in cell walls, nuclei, and in filamentous structures associated with ribosomes as visualized by immuno-electron microscopy. Five isotypes (pI 5.8, 6.0, 6.3, 6.6, 6.8) of this enzyme were found, isolated and their biochemical characteristics determined. The molecular mass of these isotypes slightly increased as their pI values became smaller. The relative abundance of these isotypes differed in different subcellular fractions. This apyrase has many phosphorylation (17 sites) and other modification sites (7 sites), and may be modified in various ways to furnish different isoforms with different functions and locations. This apyrase is encoded by single gene, which produced mRNAs with different lengths in the 3E untranslated region (3EUTR), and therefore the 3EUTR might also be important to transport these mRNAs to different subcellular locations.