Abnormal metabolites of isoleucine in a patient with propionyl‐CoA carboxylase deficiency

A number of previously unrecognized abnormal metabolites have been identified and quantitated in the urine of a patient with an inherited deficiency of propionyl‐CoA carboxylase. These included the isoleucine metabolites 2‐methyl‐3‐hydroxybutyric acid and 2‐methylacetoacetic acid. The isomers 3‐hydroxyvaleric acid and 3‐oxovaleric acid were found, which may be products of the condensation of propionyl‐CoA with acetyl‐CoA catalyzed by 3‐oxoacyl‐CoA thiolases. Following a load of isoleucine, 2‐methylbutyrylglycine was identified. This metabolite has not previously been observed in man.