D. melanogaster produces 3 different polyamines: putrescine, spermidine and spermine. Their biosynthesis occurs in the cytosol and begins with the decarboxylation of L-ornithine to putrescine, followed by the sequential addition of an aminopropyl group to produce spermidine and spermine. Polyamines can be secreted or transported into other organelles, such as the nucleus. Their charge and flexibility allow polyamines to bind nucleic acids, proteins and acidic phospholipids, thus playing a role in maintaining chromatin structure, membrane stability, scavenging free radicals and the regulation of ion channels. Spermidine is also a substrate for the post-translational hypusination of a conserved lysine residue in eukaryotic translation elongation factor 5 (eEF5). (Adapted from FBrf0265050 and PMID:37018845.)