Polyamine
A polyamine is an organic compound having two or more primary amino groups –NH2.
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–)2–H, and spermine H2N–((CH2)4–NH–)3–H.
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.[1]
Cyclen is the main representative of a class of cyclic polyamines. Polyethylene amine is a polymer based on aziridine monomer.
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[edit] Functions
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. [2]
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.[3]
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.
Polyamines can enhance the permeability of the blood-brain barrier.[4]
They are involved in modulating senescence of organs in plants and are therefore considered as a plant hormone.[5]
[edit] Synthesis of linear polyamines
[edit] Putrescine
Putrescine is synthesized biologically via two different pathways, both starting from arginine.
- 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).
[edit] Cadaverine
Cadaverine is synthesized from lysine in a one-step reaction with lysine decarboxylase (LDC).
[edit] Spermidine and spermine
Spermidine is synthesized from putrescine, using an aminopropylic group from decarboxylated S-adenosyl-L-methionine (SAM). The reaction is catalyzed by spermidine synthase.
Spermine is synthesized from the reaction of spermidine with SAM in the presence of the enzyme spermine synthase .
[edit] References
- ^ Lawrence, Stephen A. (2004). Amines: synthesis, properties and applications. Cambridge University Press. p. 64. ISBN 978-0-521-78284-5. http://books.google.com/books?id=35xwBwjhe2MC&pg=PA64.
- ^ 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.
- ^ 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.
- ^ 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. http://pubs.acs.org/doi/abs/10.1021/jm801481y.
- ^ 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. PMID 11022232. http://www.springerlink.com/content/r59701458272g088/.
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