title: UVB photoprotective role of mycosporines in yeast: photostability and antioxidant activity of mycosporine-glutaminol-glucoside.
abstract: Several yeast species are able to synthesize and accumulate UV-radiation-absorbing mycosporine metabolites that are of unclear physiological function. In this work we analyzed the relationship between mycosporine-glutaminol glucoside (MGG) production, cell survival after UVB irradiation, and formation of cyclobutane pyrimidine dimers (CPDs). We also assessed the photostability and singlet oxygen quenching activity of MGG. A set of nine isolates of the basidiomycetous yeast Cryptococcus steppossus cultured in both dark and light conditions was used for the studies. Survival of the UVB-irradiated isolates and MGG concentration had a linear relationship when the concentration was over 2.5 mg g(-1). CPD accumulation and MGG accumulation were inversely related. MGG in aqueous solution was photostable with a photodecomposition quantum yield of 1.16 × 10(-5). MGG quenching of singlet oxygen was also observed, and the rate constant for the process in D(2)O was 5.9 × 10(7) M(-1) s(-1). Our results support the idea that MGG plays an important role as a UVB photoprotective metabolite in yeasts by protecting against direct damage on DNA and probably against indirect damage by singlet oxygen quenching.
authors.affiliation: Laboratorio de Microbiología Aplicada y Biotecnología, Instituto de Investigaciones en Biodiversidad y Medio Ambiente, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional del Comahue, Bariloche, Argentina.
authors.forename: Martín
authors.initials: M
authors.lastname: Moliné
authors.forename: Ernesto M
authors.initials: EM
authors.lastname: Arbeloa
authors.forename: María R
authors.initials: MR
authors.lastname: Flores
authors.forename: Diego
authors.initials: D
authors.lastname: Libkind
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Farías
authors.forename: Sonia G
authors.initials: SG
authors.lastname: Bertolotti
authors.forename: María Sandra
authors.initials: MS
authors.lastname: Churio
authors.forename: María Rosa
authors.initials: MR
authors.lastname: van Broock
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D003454:Cryptococcus / Q000378:metabolism / Q000528:radiation effects*; D003511:Cyclohexanols / Q000737:chemistry / Q000378:metabolism*; D004249:DNA Damage; D005960:Glucosides / Q000737:chemistry / Q000378:metabolism*; D011740:Pyrimidine Dimers / Q000378:metabolism; D026082:Singlet Oxygen / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D003511:Cyclohexanols; D005960:Glucosides; D011740:Pyrimidine Dimers; C474430:mycosporine-glutamicol-glucoside; D026082:Singlet Oxygen