The ubiquinone obtained from E. coli after feeding of 1-deoxy[3-2H]xylulose shows labeling of the E-methyl group in the terminal unit and of all other positions derived from the terminal methylene group of isopentenyl pyrophosphate, whilst label from 1-deoxy[4-2H]xylulose is retained exclusively in the double bond corresponding to the dimethylallyl pyrophosphate starter unit.
