title: Functional diversity inside the Arabidopsis polyamine oxidase gene family.
abstract: Polyamine oxidases (PAOs) are FAD-dependent enzymes involved in polyamine catabolism. All so far characterized PAOs from monocotyledonous plants, such as the apoplastic maize PAO, oxidize spermine (Spm) and spermidine (Spd) to produce 1,3-diaminopropane, H(2)O(2), and an aminoaldehyde, and are thus considered to be involved in a terminal catabolic pathway. Mammalian PAOs oxidize Spm or Spd (and/or their acetyl derivatives) differently from monocotyledonous PAOs, producing Spd or putrescine, respectively, in addition to H(2)O(2) and an aminoaldehyde, and are therefore involved in a polyamine back-conversion pathway. In Arabidopsis thaliana, five PAOs (AtPAO1-AtPAO5) are present with cytosolic or peroxisomal localization and three of them (the peroxisomal AtPAO2, AtPAO3, and AtPAO4) form a distinct PAO subfamily. Here, a comparative study of the catalytic properties of recombinant AtPAO1, AtPAO2, AtPAO3, and AtPAO4 is presented, which shows that all four enzymes strongly resemble their mammalian counterparts, being able to oxidize the common polyamines Spd and/or Spm through a polyamine back-conversion pathway. The existence of this pathway in Arabidopsis plants is also evidenced in vivo. These enzymes are also able to oxidize the naturally occurring uncommon polyamines norspermine and thermospermine, the latter being involved in important plant developmental processes. Furthermore, data herein reveal some important differences in substrate specificity among the various AtPAOs, which suggest functional diversity inside the AtPAO gene family. These results represent a new starting point for further understanding of the physiological role(s) of the polyamine catabolic pathways in plants.
authors.affiliation: Department of Biology, University Roma Tre, 00146 Rome, Italy. tavlador@uniroma3.it
authors.forename: Paola
authors.initials: P
authors.lastname: Fincato
authors.forename: Panagiotis N
authors.initials: PN
authors.lastname: Moschou
authors.forename: Valentina
authors.initials: V
authors.lastname: Spedaletti
authors.forename: Raffaela
authors.initials: R
authors.lastname: Tavazza
authors.forename: Riccardo
authors.initials: R
authors.lastname: Angelini
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Federico
authors.forename: Kalliopi A
authors.initials: KA
authors.lastname: Roubelakis-Angelakis
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Tavladoraki
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity; D000097667:Polyamine Oxidase
chemical_list: D029681:Arabidopsis Proteins; D000587:Oxidoreductases Acting on CH-NH Group Donors; D000097667:Polyamine Oxidase