Secondary metabolite
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Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of organisms.[1] Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's survivability, fecundity, or aesthetics, or perhaps in no significant change at all. Secondary metabolites are often restricted to a narrow set of species within a phylogenetic group.[2] Secondary metabolites often play an important role in plant defense against herbivory[3] and other interspecies defenses.
Categories
Most of the secondary metabolites of interest to humankind fit into categories which classify secondary metabolites based on their biosynthetic origin. Since secondary metabolites are often created by modified primary metabolite synthases, or "borrow" substrates of primary metabolite origin, these categories should not be interpreted as saying that all molecules in the category are secondary metabolites (for example the steroid category), but rather that there are secondary metabolites in these categories.
Small "small molecules"
- Alkaloids (usually a small, heavily derivatized amino acid):
- Hyoscyamine, present in Datura stramonium
- Atropine, present in Atropa belladonna, Deadly nightshade
- Cocaine, present in Erythroxylon coca the Coca plant
- Codeine and Morphine, present in Papaver somniferum, the opium poppy
- Tetrodotoxin, a microbial product in Fugu and some salamanders
- Vincristine & Vinblastine, mitotic inhibitors found in the Rosy Periwinkle
- Terpenoids (come from semiterpene oligomerization):
- Azadirachtin, (Neem tree)
- Artemisinin, present in Artemisia annua Chinese wormwood
- tetrahydrocannabinol, present in cannabis sativa
- Steroids (Terpenes with a particular ring structure)
- Saponins (plant steroids, often glycosylated)
- Glycosides (heavily modified sugar molecules):
- Phenols:
- Phenazines:
- Pyocyanin
- Phenazine-1-carboxylic acid (and derivatives)
Big "small molecules", produced by large, modular, "molecular factories"
- Polyketides:
- Fatty acid synthase products :
- FR-900848
- U-106305
- phloroglucinols
- Nonribosomal peptides:
- Hybrids of the above three:
- Polyphenols
Non-"small molecules" - DNA, RNA, ribosome, or polysaccharide "classical" biopolymers
- Ribosomal peptides:
- Microcin-J25
See also
- Secondary metabolism
- Hairy root culture, a strategy used in plant tissue culture to produce good quantities of valuable secondary metabolites
References
- ^ Fraenkel, Gottfried S. (1959). "The raison d'Etre of secondary plant substances". Science. 129: 1466–1470.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ "Chemical plants". Retrieved 2008-12-19.
- ^ Stamp, Nancy (2003). "Out of the quagmire of plant defense hypotheses". The Quarterly Review of Biology. 78 (1): 23–55.
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