polyamiinit

Polyamiinit, or polyamines, are low-molecular-weight organic cations containing two or more primary amino groups. They are found in all living cells and are essential for growth, differentiation, and various cellular processes. The most abundant polyamines in many cells are putrescine, spermidine, and spermine, with cadaverine and thermospermine present in some organisms and tissues.

Biosynthesis and metabolism proceed through a coordinated pathway. Ornithine decarboxylase converts ornithine to putrescine; then spermidine synthase adds an aminopropyl group donated by decarboxylated S-adenosylmethionine to form spermidine, followed by spermine synthase adding another aminopropyl unit to produce spermine. Polyamine levels are tightly regulated at multiple levels, including transcription, translation, and enzyme activity. Catabolic routes involve acetylation by SSAT and oxidation by polyamine oxidases, which can interconvert polyamines and generate reactive byproducts. Cellular uptake occurs via specific transport systems that move polyamines across membranes.

Functions of polyamiinit are diverse. They help stabilize nucleic acid structures, influence RNA processing and translation, and modulate chromatin architecture and gene expression. They also participate in signal transduction, ion channel regulation, autophagy, and stress responses. In plants, polyamines contribute to growth, flowering, and tolerance to abiotic stress, while in animals they support cell proliferation and tissue repair.

Clinical and nutritional aspects include altered polyamine metabolism in cancer and other diseases. Inhibitors of ornithine decarboxylase have been explored as anticancer agents, and some research investigates potential anti-aging effects of polyamines such as spermidine. Dietary intake from meat, dairy, and certain vegetables contributes to tissue levels. Polyamine concentrations can be measured by analytical techniques such as HPLC or LC-MS in research settings.