title: Ultraviolet photoproducts of tryptophan can act as dioxin agonists.
abstract: Tryptophan (TRP) has been implicated in the mechanism of induction of microsomal aryl hydrocarbon hydroxylase (AHH) activity by UV light. UV irradiation of TRP resulted in formation of chloroform-soluble photoproducts that can specifically bind to the Ah receptor (AhR), an intracellular protein that mediates the induction of AHH activity by xenobiotics. Gel retardation analysis revealed that the TRP photoproducts, like other AHH inducers, complex to its specific DNA recognition site. Transient transfection experiments also demonstrated that the photoproducts could induce gene expression in an AhR-dependent manner. Thus, induction of AHH activity by UV light could be attributed, at least in part, to the formation of TRP photoproducts, which appear to act as AhR ligands.
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, East Lansing 48824-1224.
authors.forename: W G
authors.initials: WG
authors.lastname: Helferich
authors.forename: M S
authors.initials: MS
authors.lastname: Denison
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D004247:DNA / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D006168:Guinea Pigs; D008297:Male; D010777:Photochemistry; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000187:drug effects* / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D014364:Tryptophan; D004247:DNA; D001189:Aryl Hydrocarbon Hydroxylases; D000469:Alkaline Phosphatase