The metabolism of BCAA is linked with the synthesis of alanine, glutamate, and glutamine [33]. Because of impaired metabolism of BCAA in MSUD mice, and to further characterize the abnormal biochemistry in this model, we analyzed the blood levels of the alanine, glutamate, and glutamine. As shown in Table 1, the levels of all three amino acids in homozygous mice were markedly lower than the levels in +/+ or +/- mice. The levels of these amino acids in the +/- mice were comparable to those in +/+ mice (Table 1). Because of the abnormal decrease in the blood alanine level and marked rise in blood BCAA levels that are characteristic of MSUD, a recent report on MSUD patients has suggested that the ratio of BCAA/alanine provides a more sensitive measure of the abnormal biochemistry of MSUD than BCAA level alone [8]. Therefore, we also expressed the amino acid results as BCAA/alanine ratio. As shown in Figure 2C, this ratio in -/- pups was more than 6-fold higher than +/+ or +/- littermates. These blood amino acid results are consistent with the concentrations seen in patients with MSUD [1,8,15].