Plant amine oxidases "on the move": an update.

Amine oxidases (AOs) catalyse the oxidative de-amination of polyamines, ubiquitous polycationic compounds involved in important events of cell life. They include the copper-containing amine oxidases (CuAOs; EC 1.4.3.6) and the flavin-containing polyamine oxidases (PAOs; EC 1.5.3.11). The main physiological role of these moonlighting proteins has been linked to compartment-specific H2O2 synthesis in different phases of development and differentiation as well as in the course of defence mechanisms against pathogens and abiotic stress. Moreover, several studies evidenced a correlation of AO expression levels with physiological stages characterized by intense metabolism, such as cell division or organ formation, thus leaving open the hypothesis that AOs may have also a role in the regulation of cell cycle through the modulation of polyamine cellular content. This update will deal with recent reports on the involvement of CuAOs and PAOs in abiotic (salt) stress, wound-healing and host-pathogen interactions.