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 3.6.1.5) 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.