POLYAMINE OXIDASE; PAOX

Alternative titles; symbols

• PAO

HGNC Approved Gene Symbol: PAOX

Cytogenetic location: 10q26.3 Genomic coordinates (GRCh38): 10:133,379,261-133,391,693 (from NCBI)

▼ Description
The polyamines spermidine and spermine are assembled by sequential transfer of aminopropyl units onto a core diamine unit, putrescine. In the polyamine back-conversion pathway, the same aminopropyl units are removed from spermine and spermidine by sequential acetylation followed by oxidation. PAOX is an FAD-dependent polyamine oxidase (EC 1.5.3.11) that functions in the polyamine back-conversion pathway (summary by Vujcic et al., 2003).

▼ Cloning and Expression
By searching databases for sequences similar to human spermine oxidase (SMOX; 615854), Vujcic et al. (2003) identified PAOX, which they called PAO. The deduced 511-amino acid protein has a calculated molecular mass of 55.5 kD and shares 39% identity with SMOX. Vujcic et al. (2003) also identified mouse Pao, which encodes a deduced 504-amino acid protein that shares 81% identity with human PAO. EST database analysis detected PAO expression in brain, eye, kidney, ovary, and prostate, as well as in several neoplasias.

Wu et al. (2003) determined that the mouse Pao protein has 2 conserved FAD-binding regions and a C-terminal peroxisomal targeting signal sequence. PCR analysis detected variable Pao expression in all adult mouse tissues examined, with highest expression in liver and stomach. Expression of Pao increased with development in embryonic mice.

▼ Gene Function
Using transfected HEK293 cells, Vujcic et al. (2003) found that human PAO showed FAD-dependent oxidation of N(1)-acetylspermine to form spermidine and that it released 3-acetamidopropanal and hydrogen peroxide. PAO showed similar kinetics in the oxidation of N(1)-acetylspermidine to form putrescine. With monoethyl- and diethylspermine analogs, PAO cleaved the substrate internally and adjacent to a secondary amine. PAO showed much weaker activity in the oxidation of N(1),N(12)-diacetylspermine and very low activity against spermine. Spermidine was not a PAO substrate. Mouse Pao showed similar kinetics and substrate preferences.

Independently, Wu et al. (2003) found that recombinant mouse Pao oxidized N(1)-acetylspermine to spermidine and 3-acetamidopropanal. It also oxidized N(1)-acetylspermidine to putrescine and 3-acetamidopropanal.

▼ Mapping
By genomic sequence analysis, Vujcic et al. (2003) mapped the PAOX gene to chromosome 10.

Hartz (2014) mapped the PAOX gene to chromosome 10q26.3 based on an alignment of the PAOX sequence (GenBank AL834535) with the genomic sequence (GRCh37).

Wu et al. (2003) stated that the mouse Paox gene maps to chromosome 7F4.