Disorders of Branched-Chain Amino Acid Metabolism

In the metabolism of L-leucine, the isovaleryl-CoA produced by the oxidative decarboxylation step is further metabolized by a series of enzyme-catalysed steps to acetoacetate and acetyl-CoA and thence into the tricarboxylic acid cycle. Specific enzyme deficiencies at every stage of this metabolic pathway are known and are described in Section 10.3. In contrast, only one disorder of L-isoleucine metabolism subsequent to the oxidative decarboxylation step has been recognized (Section 10.4), and no disorders of the L-valine pathway from isobutyryl-CoA have been described. This may be due to their relative rarity but possibly also to greater difficulty in their detection. The metabolism of valine and leucine is, however, of particular interest in the organic acidurias, since both are major precursors of propionyl-CoA and methylmalonyl-CoA, defects in the metabolism of which lead to propionic acidaemia and methylmalonic aciduria (Chapter 11). 

This chapter is concerned with the known disorders in the metabolism of the branched-chain amino acids after the initial transamination step, that lead to abnormal organic aciduria. Disorders of propionate and methylmalonate metabolism are discussed separately in Chapter 11. 

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Disorders of Branched Chain Amino Acid Metabolism... 

Disorders of branched-chain amino acid metabolism... 

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