This class of compounds includes several synthetic substances that are important feedstocks for the chemical industry, such as ethylene diamine H2N–CH2–CH2–NH2, 1,3-diaminopropane H2N–(CH2)3–NH2, and hexamethylenediamine H2N–(CH2)6–NH2. It also includes many substances that play important roles in both eukaryotic and prokaryotic cells, such as putrescine H2N–(CH2)4–NH2, cadaverine H2N–(CH2)5–NH2, spermidine H2N–(CH2)4–NH–(CH2)3–NH2, and spermine H2N–(CH2)3–NH–(CH2)4–NH–(CH2)3–NH2.
As of 2004, there had been no reports of any geminal diamine, a compound with two or more unsubstituted –NH2 groups on the same carbon atom. However, substituted derivatives are known, such as tetraethylmethylenediamine, (C2H5)2N–CH2–N(C2H5)2.
Though it is known that polyamines are synthesized in cells via highly regulated pathways, their actual function is not entirely clear. As cations, they bind to DNA, and, in structure, they represent compounds with cations that are found at regularly spaced intervals (unlike, say, Mg2+ or Ca2+, which are point charges). They have also been found to act as promoters of programmed ribosomal frameshifting during translation.
If cellular polyamine synthesis is inhibited, cell growth is stopped or severely retarded. The provision of exogenous polyamines restores the growth of these cells. Most eukaryotic cells have a polyamine transporter system on their cell membrane that facilitates the internalization of exogenous polyamines. This system is highly active in rapidly proliferating cells and is the target of some chemotherapeutics currently under development.
Polyamines are also important modulators of a variety of ion channels, including NMDA receptors and AMPA receptors. They block inward-rectifier potassium channels so that the currents of the channels are inwardly rectified, thereby the cellular energy, i.e. K+ ion gradient across the cell membrane, is conserved. In addition, polyamine participate in initiating the expression of SOS response of Colicin E7 operon and down-regulate proteins that are essential for colicin E7 uptake, thus conferring a survival adventage on colicin-producing E. coli under stress conditions.
Synthesis of linear polyamines 
- In one pathway, arginine is converted into agmatine, with a reaction catalyzed by the enzyme arginine decarboxylase (ADC); then agmatine is transformed into carbamilputrescine by agmatine imino hydroxylase (AIH). Finally, carbamilputrescine is converted into putrescine.
- In the second pathway, arginine is converted into ornithine and then ornithine is converted into putrescine by ornithine decarboxylase (ODC).
Spermidine and spermine 
Polyamine Analogues 
The critical role of polyamines in cell growth has led to the development of a number of agents that interfere with polyamine metabolism. These agents are used in cancer therapy. Polyamine analogues upregulate p53 in a cell leading to restriction of proliferation and apoptosis. It also decreases the expression of estrogen receptor alpha in ER positive breast cancer
- Lawrence, Stephen A. (2004). Amines: synthesis, properties and applications. Cambridge University Press. p. 64. ISBN 978-0-521-78284-5.
- Rato C, Amirova S.R, Bates D.G, Stansfield I, Wallace H.M (June 2011). "Translational recoding as a feedback controller: systems approaches reveal polyamine-specific effects on the antizyme ribosomal frameshift". Nucleic Acid Res. 39 (11): 4587–4597. doi:10.1093/nar/gkq1349. PMC 3113565. PMID 21303766.
- Wang C, Delcros JG, Cannon L et al. (November 2003). "Defining the molecular requirements for the selective delivery of polyamine conjugates into cells containing active polyamine transporters". J. Med. Chem. 46 (24): 5129–38. doi:10.1021/jm030223a. PMID 14613316.
- Yi-Hsuan Pan, Chen-Chung Liao (May 2006). "The critical roles of polyamines regulating ColE7 production and restricting ColE7 uptake of the colicin-producing Escherichia coli". JBC 281: 13083–13091. PMID 16549429.
- Zhang L, Lee HK, Pruess TH, White HS, Bulaj G (March 2009). "Synthesis and applications of polyamine amino acid residues: improving the bioactivity of an analgesic neuropeptide, neurotensin". J. Med. Chem. 52 (6): 1514–7. doi:10.1021/jm801481y. PMC 2694617. PMID 19236044.
- Pandey S, Ranade SA, Nagar PK, Kumar N (September 2000). "Role of polyamines and ethylene as modulators of plant senescence". J. Biosci. 25 (3): 291–9. doi:10.1007/BF02703938. PMID 11022232.
- "Polyamine analogue induced growth restricion". Retrieved 21 November 2012.
- "Polyamine analogues down-regulate estrogen receptor alpha expression in human breast cancer cells". Retrieved 21 November 2012.
- Polyamines in cell cycle proliferation and cell death
- Ornithine Decarboxylase: Expression and regulation in rat brain and in transgenic mice, 2002, Pekka Kilpelainen, Department of Biochemistry, University of Oulu. Extensive review of literature through 2001 on polyamine structure, properties, metabolism in mammals, and physiological and pathophysiological roles (See article Table of Contents)