AN INTERMEDIATE IN THE CONVERSION OF p-HYDROXYBENZOATE-U-C 14 TO UBIQUINONE IN RHODOSPIRILLUM RUBRUM

Abstract

When suspensions of washed R. rubrum are incubated with p-hydroxy-benzoate-U-C14, C14 is incorporated into ubiquinone and a new substance, designated as "compound-X." C14 appears more rapidly in compound-X than in ubiquinone. Ubiquinone formation occurs either anaerobically in the light or aerobically in the dark. Air inhibits in light and light inhibits the aerobic process. The accumulation of C14 in compound-X is less sensitive to changes of these variables. If the incubation is conducted anaerobically in the dark, compound-X but not ubiquinone becomes highly labeled. Endogenous compound-X is converted to ubiquinone and rhodo-quinone when the cells taken from this incubation are washed free of radioactive substrate, resuspended, and incubated anaerobically in the lights. C14 is also incorporated into compound-X from acetate-1-Cl4 and -2-C14 but not from p-hydroxybenzoate-carboxyl-C14 or methionine-methyl-C14. Ozonolysis yields radioactive levulin-aldehyde from compound-X labeled from acetate-2-C14. These data suggest that compound-X is a benzenoid or quinonoid compound with an isoprenoid side chain and without methoxyl groups.