Schematic representation of polyamine catabolic pathways in Arabidopsis. (A) In the cell wall, Put and Spd can be oxidatively deaminated by CuAOs (ATAO1 and AtCuAO1) to produce the corresponding aminoaldehydes, H2O2 and NH3. (B) In peroxisomes, Spm and Spd are substrates for PAOs (PAO2-4) that catalyse the sequential back-conversion of Spm to Spd and Spd to Put, which is subjected to feedback inhibition by its end product, Put. CuAOs (AtCuAO2 and AtCuAO3) can catalyse the terminal oxidation of Put and Spd. The oxidation product of Put, 4-aminobutanal, can be a substrate for peroxisomal BADH (ALDH10A9), which catalyses its conversion to GABA. (C) In the cytosol, AtPAO1, and probably AtPAO5, oxidize Spm and Spd by the back-conversion pathway. Some AtCuAOs, annotated as cytosolic in TAIR, could mediate terminal PA catabolism in this cellular compartment.
Planas-Portell et al. BMC Plant Biology 2013 13:109 doi:10.1186/1471-2229-13-109