Molecular analysis of a patient with carnitine palmitoyltransferase II deficiency

Carnitine palmitoyltransferase (CPT), one of the key enzymes of β- oxidation, translocates long-chain fatty acids from the cytosolic compartment into the mitochondrial matrix to undergo β-oxidation. Recently, the CPT system has been characterized to consist of two distinct mitochondrial membrane-bound enzymes, CPT I, located on the inner side of the outer mitochondrial membrane, and CPT II, located on the inner mitochondrial membrane. We have investigated a Japanese patient with muscular manifestations who was previously reported as CPT deficiency. Enzymatic analysis of her cultured lymphoblasts revealed that CPT II activity was reduced to 5.8%, indicating that the patient suffered from CPT II deficiency. Molecular analysis identified a missense mutation, a glutamate (174)-to- lysine substitution (E174K), in the CPT II cDNA. The patient was homozygous for the mutation. The presence of the mutation was confirmed by PCR-RFLP with a mismatched primer to generate Mbo II recognition sequence at the mutation site. It has been reported that CPT II deficiency manifests as two different clinical phenotypes: a muscular form and a hepatocardiomuscular form. To our knowledge, this is the first case of CPT II deficiency with muscular symptoms to be characterized by molecular analysis in Japan.