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Lyngbyatoxin-a
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Lyngbyatoxin-a is a cyanotoxin produced by certain cyanobacteria species, most notably ''Moorea producens'' (formerly ''Lyngbya majuscula''). It is produced as defense mechanism to ward of any would-be predators of the bacterium, being a potent blister agent as well as carcinogen. Low concentrations cause a common skin condition known as seaweed dermatitis.〔Cardellina JH 2nd, Marner FJ, Moore RE. Seaweed dermatitis: structure of lyngbyatoxin A. ''Science''. 1979 Apr 13;204(4389):193-5. PMID 107586〕〔Fujiki H, Mori M, Nakayasu M, Terada M, Sugimura T, Moore RE. Indole alkaloids: dihydroteleocidin B, teleocidin, and lyngbyatoxin A as members of a new class of tumor promoters. ''Proceedings of the National Academy of Sciences USA''. 1981 Jun;78(6):3872-6. PMID 6791164〕〔Kozikowski AP, Shum PW, Basu A, Lazo JS. Synthesis of structural analogues of lyngbyatoxin A and their evaluation as activators of protein kinase C. ''Journal of Medicinal Chemistry''. 1991 Aug;34(8):2420-30. PMID 1875340〕〔Osborne NJ, Webb PM, Shaw GR. The toxins of Lyngbya majuscula and their human and ecological health effects. ''Environment International''. 2001 Nov;27(5):381-92. PMID 11757852〕〔Ito E, Satake M, Yasumoto T. Pathological effects of lyngbyatoxin A upon mice. ''Toxicon''. 2002 May;40(5):551-6. PMID 11821127〕〔Edwards DJ, Gerwick WH. Lyngbyatoxin biosynthesis: sequence of biosynthetic gene cluster and identification of a novel aromatic prenyltransferase. ''Journal of the American Chemical Society''. 2004 Sep 22;126(37):11432-3. PMID 15366877〕
== Biosynthesis ==
Lyngbyatoxin is a terpenoid indole alkaloid that belongs to the class of non-ribosomal peptides (NRP). Lyngbyatoxin contains a nucleophilic indole ring that takes part in the activation of protein kinases. Figure 1, shows the biosynthesis of Lyngbyatoxin reported by Neilan et. al and Gerwick et. al.The non-ribosomal peptide synthase (NRPS) LtxA protein condenses L-methyl-valine and L-tryptophan to form the linear dipeptide N-methyl-L-valyl-L-tryptophan. The latter is released via a NADPH-dependent reductive cleavage to form the aldehyde which is subsequently reduced to the corresponding alcohol. Then LtxB which is a P450-dependent monooxygenase serves as a catalyst in the oxidation and subsequent cyclization of N-methyl-L-valyl-L-tryptophan.Finally, LtxC which is a reverse prenyltransferase performs the transfer of a geranyl pyrophosphate (GPP) to carbon-7 of the indole ring which is accompanied by the lost of pyrophosphate.
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