The AUH gene codes for the mitochondrial enzyme, 3-methyglutaconyl-CoA hydratase, which in turn, plays a major role in the metabolism of leucine. Specifically, this enzyme catalyzes the conversion of 3-methylglutaconyl-CoA to 3-hydroxy-3-methylglutaryl-CoA. Defects in this gene and the resultant deficiency of the enzyme activity lead to the build-up of toxic metabolites of alternate leucine break-down pathways, such as 3 methylglutaconic acid.