Fatty Maple syrup disease

The branched fatty acids the oxidation of which will be considered now are carbon compounds derived from amino acid metabolism. Isovalerate, methylbu-tyrate, and isobutyrate are related to the metabolism of leucine, isoleucine, and valine, respectively. The interest in the metabolism of branched fatty acids stems partly from the fact that the branched amino acids from which they are derived are precisely those that accumulate in maple syrup disease. 

The catabolism of leucine, valine, and isoleucine presents many analogies to fatty acid catabolism. Metabolic disorders of branched-chain amino acid catabolism include hypervalinemia, maple syrup urine disease, intermittent branched-chain ketonuria, isovaleric acidemia, and methylmalonic aciduria. 

Polled hereford calves in Australia develop maple syrup urine disease relatively often/ 6 One cause was established as a mutation that introduces a stop codon that causes premature termination within the leader peptide during synthesis of the thiamin diphosphate-dependent El subunit. A similar biochemical defect in a mutant of Bacillus subtilis causes difficulties for this bacterium, which requires branched-chain fatty acids in its membranes. Branched acyl-CoA derivatives are needed as starter pieces for their synthesis (Chapter 29). With the oxidative decarboxylation of the necessary oxoacids blocked, the mutant is unable to grow unless supplemented with branched-chain fatty acids. 

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