Mechanism of Photoregulated Carotenogenesis in Rhodotorula

近紫外光（近UV）照射的影响，记录在红色酵母Rhodotorula minuta，形成类胡萝卜素作为额外的响应光处理。辐照暗生长的细胞后，完整细胞和酵母细胞膜的紫外吸收光谱立即发生变化，完整细胞在短时间辐照后，在260 ~ 300 nm波长范围内吸光度降低，而在260 nm以下波长处吸光度升高，这取决于辐照的光剂量。膜组分在230 nm处的吸光度显著增加，在260 - 300 nm处的吸光度显著降低，在265、272、282、295 nm处有吸收峰。通过测定光处理膜中麦角甾醇的含量，证实了光处理膜中麦角甾醇的光化学变化是膜中麦角甾醇发生光化学变化的原因，并通过光处理膜中麦角甾醇光化学变化的作用光谱，阐明了光诱导胡萝卜素生成与麦角甾醇变化的关系。结果表明，麦角甾醇是一种光感受器，也是参与微小红酵母光诱导胡萝卜素合成的光化学反应底物。

The effect of near ultraviolet light (near-UV) irradiation were recorded spectrophotometrically in the red yeast Rhodotorula minuta, which forms carotenoids as additional response to the light treatment. Irradiation of dark-growm cells immediately caused changes in UV absorption spectrum of intact cells as well as of membrane preparations from the yeast cells.In intact cell, irradiation of a short period resulted in a decrease in the absorbance at wavelengths in the range from 260 to 300nm and a increase at wavelengths below 260nm depending on light dose of irradiation. Membrane fractions responded to irradiation by a striking increase in absorbance at 230nm and decrease at 260 - 300nm with the peaks at 265, 272, 282, 295nm. It was confirmed by the determination of ergosterol contents of light treated membrane that the absorbance changes observed in membrane preparations were attributed to a photochemical change of ergostrol in the membrane.Action spectrum for photochemical change of ergosterol in membrane preparation to make clear the relationship between the photoinduction of carotenogenesis and ergosterol change. The action spectrum obtained was extremely approximated by the action spectrum for photoinduction of carotenogenesis reported previously.These results strongly suggested that ergosterol was a photoreceptor and a substrate for photochemical reaction involved in the photoregulated carotenogenesis in the yeast Rhodotorula minuta.