Biochem/physiol Actions

Isovalerylcarnitine is the phenotypic abnormality in iso-valeric acidemia resulting from an accumulation of isovaleric acid, which is toxic to the central nervous system. Isovaleric acidemia is an autosomal recessive inborn error of leucine metabolism caused by a deficiency of the mitochondrial enzyme isovaleryl-CoA dehydrogenase resulting in the accumulation of derivatives of isovaleryl-CoA. It was the first organic acidemia recognized in humans and can cause significant morbidity and mortality. Early diagnosis and treatment with a protein restricted diet and supplementation with carnitine and glycine are effective in promoting normal development in severely affected individuals. An alternative pathway through glycine-N-acylase allows detoxification by producing isovaleryl-glycine, which is excreted. Thus, isovalerylcarnitine and isovalerylglycine are the hallmarks of this disorder in plasma and urine, respectively, and are elevated regardless of a patient′s metabolic condition.