title: Singlet oxygen and peroxyl radicals regulate carotenoid biosynthesis in Phaffia rhodozyma.
abstract: Carotenoids have recently received considerable interest because of their potential in delaying or preventing degenerative diseases such as arteriosclerosis, cancer, and aging. In this study we show that the active oxygen species singlet oxygen (1O2) and peroxyl radicals differently affect carotenoid composition and biosynthesis in the yeast Phaffia rhodozyma. Photochemical generation of 1O2 with rose bengal or alpha-terthienyl induced carotenoid accumulation. In contrast, peroxyl radicals derived from t-butylhydroperoxide (tBOOH) or H2O2 decreased the content of astaxanthin and increased beta-carotene by approximately 4-fold, suggesting end product feedback regulation by astaxanthin or inhibition of biosynthetic enzymes. 14C labeling of carotenoids during oxidative stress supported the possibility of end product regulation. Carotenoids were bleached by 8 mM tBOOH within 6 h when carotenogenesis was inhibited by thymol. When treated with peroxides, a previously unreported pigment in P. rhodozyma was formed. The carotenoid had a mass of 580 Da and a molecular formula of C40H52O3. Chemical derivatizations combined with mass and absorbance spectroscopy tentatively identified the carotenoid as dehydroflexixanthin (3,1'-dihydroxy-2,3,3',4'-tetradehydro-1',2'-dihydro-beta,psi-caro tene-4-one). This study provides the first report of induction of astaxanthin biosynthesis by 1O2, probable feedback control by astaxanthin, and the oxidative degradation of astaxanthin to novel pigments in P. rhodozyma.
authors.affiliation: Department of Food Microbiology and Toxicology, University of Wisconsin, Madison 53706, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Schroeder
authors.forename: E A
authors.initials: EA
authors.lastname: Johnson
mesh_terms: D002338:Carotenoids / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry; D005609:Free Radicals; D008798:Mevalonic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology*; D010545:Peroxides / Q000494:pharmacology*; D010777:Photochemistry; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D026082:Singlet Oxygen; D024341:Xanthophylls; D015003:Yeasts / Q000187:drug effects* / Q000378:metabolism; D019207:beta Carotene; D020122:tert-Butylhydroperoxide
chemical_list: D005609:Free Radicals; D010545:Peroxides; D017382:Reactive Oxygen Species; D024341:Xanthophylls; D019207:beta Carotene; D026082:Singlet Oxygen; C049375:perhydroxyl radical; D002338:Carotenoids; C015367:mevalonolactone; C005948:astaxanthine; D020122:tert-Butylhydroperoxide; D008798:Mevalonic Acid; D010100:Oxygen