spermine

Spermine is a naturally occurring polyamine, a positively charged organic molecule that carries four amino groups. It is a polycation at physiological pH and participates in many cellular processes that require interaction with negatively charged macromolecules. Spermine was first isolated from semen, a historical source that gave the molecule its name. Its chemical formula is C10H26N4 and its structure is symmetrical with two 3-aminopropyl units linked by a butane chain.

Biosynthesis: Ornithine decarboxylase converts ornithine to putrescine; spermidine synthase adds an aminopropyl group from decarboxylated S-adenosylmethionine to form spermidine; spermine synthase adds another aminopropyl group to form spermine. Decarboxylated SAM is produced by SAM decarboxylase and serves as the donor of aminopropyl units. Catabolic pathways, including polyamine oxidases, degrade spermine back to spermidine and putrescine, generating hydrogen peroxide in the process. Ornithine decarboxylase is a rate-limiting enzyme and is a common target of inhibitors used in research and therapy.

Functions: Spermine binds DNA, RNA, and various proteins, helping to stabilize chromatin structures and influence transcription and translation. It supports cell growth and proliferation and can modulate ion channels and membrane properties. It also exhibits antioxidant properties in some contexts, contributing to cellular defense against oxidative stress.

Distribution and diet: Spermine is present in many tissues, with higher levels in rapidly dividing cells and in semen. Dietary polyamines come from a range of foods (meat, fish, dairy, some vegetables), and gut microbiota can contribute to overall levels. Cellular homeostasis is maintained through uptake, synthesis, and catabolism.

Clinical relevance and research: Altered polyamine metabolism is linked to cancer and aging. Inhibitors of polyamine biosynthesis, such as ornithine decarboxylase inhibitors, have been explored as anticancer strategies. Spermine levels are also studied as potential biomarkers, with ongoing research into roles in neurodegenerative disease and other conditions.