Synthesis and characterisation of acyl glycines - Their measurement in single blood spots by gas chromatography mass spectrometry to diagnose inborn errors of metabolism

Acyl glycines are normally minor metabolites of fatty acids; however, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. Therefore measurement of these metabolites in body fluids can be used to diagnose these metabolic disorders. The chemical synthesis of a range of acyl glycines is described, together with that of their C-13(2)-isotopomers for use as internal standards. An analytical method for the measurement of hexanoyl, octanoyl, 3-phenylpropionyl and suberyl glycines in urine, employing gas chromatography-mass spectrometry with negative-ion chemical ionisation was adapted to measure a larger range of acyl glycines in a single blood spot on a standard Guthrie card. Diagnoses of a case of medium-chain acyl-CoA dehydrogenase deficiency and a case of isovaleric acidaemia were confirmed using a single blood spot from each patient.