Schroeder W A, Johnson E A
Department of Food Microbiology and Toxicology, University of Wisconsin, Madison 53706, USA.
J Biol Chem. 1995 Aug 4;270(31):18374-9. doi: 10.1074/jbc.270.31.18374.
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.
类胡萝卜素最近受到了广泛关注，因为它们具有延缓或预防诸如动脉硬化、癌症和衰老等退行性疾病的潜力。在本研究中，我们表明活性氧单线态氧（1O2）和过氧自由基对红法夫酵母中类胡萝卜素的组成和生物合成有不同的影响。用孟加拉玫瑰红或α-三联噻吩光化学产生1O2可诱导类胡萝卜素积累。相反，叔丁基过氧化氢（tBOOH）或H2O2产生的过氧自由基使虾青素含量降低，β-胡萝卜素含量增加了约4倍，这表明存在虾青素的终产物反馈调节或生物合成酶的抑制作用。氧化应激期间类胡萝卜素的14C标记支持了终产物调节的可能性。当百里香酚抑制类胡萝卜素生成时，8 mM tBOOH在6小时内使类胡萝卜素漂白。用过氧化物处理时，红法夫酵母中形成了一种以前未报道的色素。该类胡萝卜素的分子量为580 Da，分子式为C40H52O3。化学衍生化结合质谱和吸收光谱初步鉴定该类胡萝卜素为脱氢flexixanthin（3,1'-二羟基-2,3,3',4'-四脱氢-1',2'-二氢-β,ψ-胡萝卜素-4-酮）。本研究首次报道了1O2诱导红法夫酵母中虾青素生物合成、虾青素可能的反馈控制以及虾青素氧化降解为新色素的过程。
