title: Marine toxins and nonmarine toxins: convergence or symbiotic organisms?
abstract: Bioactive marine natural products occur only rarely in nonmarine sources. The converse also is true. Divergent evolutionary pathways for the biosynthesis of bioactive secondary metabolites seem to be the rule. Marine biosynthetic pathways lead to a wide variety of different structural classes, among which polyethers, macrolides, terpenes, unusual amino acids/peptides, and alkaloids are notable. Nonmarine biosynthetic pathways also lead to a similar wide variety of structural classes. However, the structures are usually quite different from the marine analogues. The alkaloids of plants are notable, but again there appears little convergence between the marine and nonmarine alkaloids. However, tetrodotoxin, a remarkable, highly polar, marine alkaloid, does occur in various amphibians. The occurrence and possible origin of tetrodotoxin and congeners, including chiriquitoxin, and of the saxitoxin analogue zetekitoxin in amphibians are reviewed.
authors.affiliation: Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892-0820, USA. jdaly@nih.gov
authors.forename: John W
authors.initials: JW
authors.lastname: Daly
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D000664:Amphibian Venoms / Q000737:chemistry*; D000818:Animals; D005397:Fish Venoms / Q000737:chemistry; D008387:Marine Toxins; D015394:Molecular Structure; D011799:Quinazolines / Q000737:chemistry; D012530:Saxitoxin / Q000031:analogs & derivatives / Q000737:chemistry; D013779:Tetrodotoxin / Q000737:chemistry; D014118:Toxins, Biological
chemical_list: D000470:Alkaloids; D000664:Amphibian Venoms; D005397:Fish Venoms; D008387:Marine Toxins; D011799:Quinazolines; D014118:Toxins, Biological; C487810:zetekitoxin AB; C059207:tetrodonic acid; D012530:Saxitoxin; D013779:Tetrodotoxin; C015741:chiriquitoxin