NOVEL GLYCINE CONJUGATES IN MEDIUM-CHAIN ACYL-COA DEHYDROGENASE-DEFICIENCY

The glycine conjugates of isocaproic, 4-methylhexanoic, 7-hydroxyoctan oic and 8-hydroxyoctanoic acids have been identified in the urine of c hildren with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency usi ng gas chromatography-mass spectrometry of the trimethylsilyl derivati ves. A quantitative study showed that the glycine conjugates of isocap roic and 4-methylhexanoic acids were excreted during acute episodes an d in smaller amounts when subjects were asymptomatic. The glycine conj ugates of 7-hydroxyoctanoic and 8-hydroxyoctanoic acids were detectabl e during acute episodes. None of the conjugates was detected in contro ls or controls receiving a diet containing medium-chain triglycerides. It is suggested that the glycine conjugates of isocaproic acid and 4- methylhexanoic acid are metabolites of branched-chain fatty acids and that they are specific for MCAD deficiency.