The ratio of 13C signal in carbon 2 relative to carbon 4 of glutamate during incorporation of [1,2-13C]-acetate. The signal intensity, determined by integration, for carbon 2 was divided by that for carbon 4 (C2/C4 ratio). Data presented are the % of the maximal ratio (obtained for wild type at 120 minutes) +/− SEM from three separate experiments. a, p < 0.05 as compared to wild type at the same time point. b, p < 0.05 as compared to other strains at the same time point.