Abstract
Postmitochondrial supernatant, cytosol, and microsomes were exposed to near-ultraviolet light and assayed for incorporation of (3H)leucine. The results indicate that near-ultraviolet light decreased the incorporation of radioactivity into the aminoacyl-tRNA fraction and into proteins. This effect depended on the wavelength of irradiation and the concentration of exposed protein. Tryptophan and epinephrine potentiated the effect of near-ultraviolet light, but catalase prevented this effect. Hydrogen peroxide decreased protein synthesis when it was added to unirradiated postmitochondrial supernatant. The results suggest that near-ultraviolet light would decrease protein synthesis by generating hydrogen peroxide from tryptophan and epinephrine.