Maple syrup urine disease metabolic pathway

Figure 20.20 Pathways of branched-chain amino acid metabolism. A, B, C, D, E, and F indicate defects in valinemia, maple syrup urine disease, isovaleric acidemia, /3-hydroxyisovaleric aciduria, a-methyl-j3-hydroxybutyric aciduria, and methylmalonic aciduria, respectively.

GlO. Goedde, H. W., and Keller, W., Metabolic pathways in maple syrup urine disease. In "Amino Acid Metabolism and Genetic Variation (W. L. Nyhan, ed.), pp. 191-214. McGraw-HiU, New York, 1967. 

Multiple deletion cannot be excluded as a possible cause of maple syrup urine disease because a deficiency in a specific decarboxylase does not adequately explain the accumulation of indole derivatives and methionine. Of course, the branched amino acids or the corresponding keto acids could inhibit other metabolic pathways. 

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