Reference "Constitutively and highly expressed Oryza sativa polyamine oxidases localize in peroxisomes and catalyze polyamine back conversion"

Reference ID

54986

Title

Constitutively and highly expressed Oryza sativa polyamine oxidases localize in peroxisomes and catalyze polyamine back conversion

Source

Amino acids, 2012, vol. 42, pp. 867-876

Authors (8)

Ono-Y	Kim-D-W
Watanabe-K	Sasaki-A
Niitsu-M	Berberich-T
Kusano-T	Takahashi-Y

Abstract

Polyamine oxidases (PAOs) are FAD-dependent enzymes involved in polyamine (PA)
catabolism. Recent studies have revealed that plant PAOs are not only active in
the terminal catabolism of PAs as demonstrated for maize apoplastic PAO but also
in a polyamine back-conversion pathway as shown for most Arabidopsis PAOs. We
have characterized Oryza sativa PAOs at molecular and biochemical levels. The
rice genome contains 7 PAO isoforms that are termed OsPAO1 to OsPAO7. Of the
seven PAOs, OsPAO3, OsPAO4, and OsPAO5 transcripts were most abundant in 2-week-
old seedlings and mature plants, while OsPAO1, OsPAO2, OsPAO6, and OsPAO7 were
expressed at very low levels with different tissue specificities. The more
abundantly expressed PAOs--OsPAO3, OsPAO4, and OsPAO5--were cloned, and their
gene products were produced in Escherichia coli. The enzymatic activities of the
purified OsPAO3 to OsPAO5 proteins were examined. OsPAO3 favored spermidine
(Spd) as substrate followed by thermospermine (T-Spm) and spermine (Spm) and
showed a full PA back-conversion activity. OsPAO4 substrate specificity was
similar to that of OsPAO5 preferring Spm and T-Spm but not Spd. Those enzymes
also converted Spm and T-Spm to Spd, again indicative of PA back-conversion
activities. Lastly, we show that OsPAO3, OsPAO4, and OsPAO5 are localized in
peroxisomes. Together, these data revealed that constitutively and highly
expressed O. sativa PAOs are localized in peroxisomes and catalyze PA back-
conversion processes.