The product of this gene is an important intermediate enzyme in polyamine biosynthesis. The polyamines spermine, spermidine, and putrescine are low molecular weight aliphatic amines essential for cellular proliferation and tumor promotion. This protein spans 22 kb comprised of 9 exons and 8 introns and encoding two species of mRNA of 2.1 and 3.4-3.6 kb originating from the use of two different polyadenylation signals. The pro protein is an approximate 38.3 kDa which is known to undergo processing at amino acid 68 to yield two fragments of 32 and 6kDa.