An Arabidopsis polyamine oxidase undergoing proteasomal regulation

"""Polyamine oxidases (PAOs) are FAD-dependent enzymes involved in polyamine catabolism. In Arabidopsis, five PAO genes (AtPAO1-5) have been identified with important differences among them in subcellular localization, substrate specificity and expression pattern, which suggest distinct physiological roles. In the present work, AtPAO5, the only so far uncharacterized AtPAO which is specifically expressed in the vascular system, was partially purified from 35S::AtPAO5-6His Arabidopsis transgenic plants and biochemically characterized. Data evidenced interesting differences in substrate specificity between AtPAO5 and the other AtPAOs. Furthermore, subcellular localization studies for AtPAO5 through confocal analysis of 35S::GFP-AtPAO5 and 35S::AtPAO5-GFP transgenic plants demonstrated cytosolic distribution of this enzyme with formation of aggregates. Treatment with the proteasomal inhibitor MG132 increased the number of aggregates, indicating AtPAO5 association with the proteasomal complex. A positive regulation of AtPAO5 expression by polyamines was also shown. These data give new insights into the complex regulatory network controlling polyamine metabolism."""