Cloning and characterization of a human polyamine oxidase that is inducible by polyamine analogue exposure

Mammalian polyamine catabolism is under the control of two enzymes, spermid ine/spermine N-1-acetyltransferase and the flavin adenine dinucleotide-depe ndent polyamine oxidase (PAO). In this study, the cloning and initial chara cterization of human PAO is reported. A 1894-bp rDNA with an open reading f rame of 1668-bp codes for a protein of 555 amino acids, In vitro transcript ion/translation of this cDNA clone produces the expected M-r 61,900 protein with PAO activity, The PAO activity of this clone is inhibited by MDL 72,5 27, a specific inhibitor of mammalian PAO, However, neither pargyline, a sp ecific monoamine oxidase inhibitor, nor semicarbazide, a specific diamine o xidase inhibitor, inhibits the PAO activity of this clone. PAO has been ref erred to as being constitutively expressed. However, 24-h exposure of a non -small cell lung carcinoma cell line, NCI H157, to 10 muM of (NN)-N-1"-bis( ethyl)norspermine results in similar to5-fold induction of PAO mRNA and a > 3-fold induction of PAO activity, These results demonstrate that in at leas t one cell type, PAO is upregulated in response to polyamine analogue expos ure. The PAO clone described here should provide a useful tool, which will facilitate the dissection of the rule of polyamine catabolism in normal gro wth and in response to the antitumor polyamine analogues.