Masayoshi Souri

Purification of human very-long-chain acyl-coenzyme A dehydrogenase and characterization of its deficiency in seven patients.

Mitochondrial very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) was purified from human liver. The molecular masses of the native enzyme and the subunit were estimated to be 154 and 70 kD, respectively. The enzyme was found to catalyze the major part of mitochondrial palmitoylcoenzyme A dehydrogenation in liver, heart, skeletal muscle, and skin fibroblasts (89-97, 86-99, 96-99, and 78-87%, respectively). Skin fibroblasts from 26 patients suspected of having a disorder of mitochondrial beta-oxidation were analyzed for VLCAD protein using immunoblotting, and 7 of them contained undetectable or trace levels of the enzyme. The seven deficient fibroblast lines were characterized by measuring acyl-coenzyme A dehydrogenation activities, overall palmitic acid oxidation, and VLCAD protein synthesis using pulse-chase, further confirming the diagnosis of VLCAD deficiency. These results suggested the heterogenous nature of the mutations causing the deficiency in the seven patients. Clinically, all patients with VLCAD deficiency exhibited cardiac disease. At least four of them presented with hypertrophic cardiomyopathy. This frequency (> 57%) was much higher than that observed in patients with other disorders of mitochondrial long-chain fatty acid oxidation that may be accompanied by cardiac disease in infants.

d-3-Hydroxyacyl-CoA Dehydratase/d-3-Hydroxyacyl-CoA Dehydrogenase Bifunctional Protein Deficiency: A Newly Identified Peroxisomal Disorder

Peroxisomal beta-oxidation proceeds from enoyl-CoA through D-3-hydroxyacyl-CoA to 3-ketoacyl-CoA by the D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxy-acyl-CoA dehydrogenase bifunctional protein (d-bifunctional protein), and the oxidation of bile-acid precursors also has been suggested as being catalyzed by the d-bifunctional protein. Because of the important roles of this protein, we reinvestigated two Japanese patients previously diagnosed as having enoyl-CoA hydratase/L-3-hydroxyacyl-CoA dehydrogenase bifunctional protein (L-bifunctional protein) deficiency, in complementation studies. We found that both the protein and the enzyme activity of the d-bifunctional protein were hardly detectable in these patients but that the active L-bifunctional protein was present. The mRNA level in patient 1 was very low, and, for patient 2, mRNA was of a smaller size. Sequencing analysis of the cDNA revealed a 52-bp deletion in patient 1 and a 237-bp deletion in patient 2. This seems to be the first report of D-bifunctional protein deficiency. Patients previously diagnosed as cases of L-bifunctional protein deficiency probably should be reexamined for a possible d-bifunctional protein deficiency.

Reversal of severe hypertrophic cardiomyopathy and excellent neuropsychologic outcome in very-long-chain acyl-coenzyme A dehydrogenase deficiency

Very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency is a disorder of fatty acid beta oxidation that reportedly has high rates of morbidity and mortality. We describe the outcome of a 5-year-old girl with VLCAD deficiency who was first seen at 5 months of age with severe hypertrophic cardiomyopathy, hepatomegaly, encephalopathy, and hypotonia. Biochemical studies indicated VLCAD deficiency caused by a stable yet inactive enzyme. Molecular genetic analysis of her VLCAD gene revealed a T1372C (F458L) missense mutation and a 1668 ACAG 1669 splice site mutation. After initial treatment with intravenous glucose and carnitine, the patient has thrived on a low-fat diet supplemented with medium-chain triglyceride oil and carnitine and avoidance of fasting. Her ventricular hypertrophy resolved significantly over 1 year, and cognitively, she is in the superior range for age. Clinical recognition of VLCAD deficiency is important because it is one of the few directly treatable causes of cardiomyopathy in children.

Medium chain 3-ketoacyl-coenzyme A thiolase deficiency: a new disorder of mitochondrial fatty acid beta-oxidation.

A Japanese male neonate died at 13 d of age after presenting at 2 d of age with vomiting, dehydration, metabolic acidosis, liver dysfunction, and terminal rabdhomyolysis with myoglobinuria. Multiple urine organic acid analyses consistently revealed a markedly elevated excretion of lactic acid, 3-hydroxybutyric acid, and saturated and unsaturated C6-C16 dicarboxylic acids, with predominant C12-C16 species. Oxidation of [1-14C]octanoic acid in cultured skin fibroblasts was significantly reduced (0.59 nmol/h/mg of protein; controls, 1.93 ± 0.65), [1-14C]palmitic acid oxidation was 1.11 nmol/h/mg of protein (controls, 1.63 ± 0.41). A systematic study of the catalytic activities of nine enzymes of the β-oxidation cycle using the respective optimal substrate revealed a deficiency of a single enzyme not previously associated with a metabolic disorder, medium chain 3-ketoacyl-CoA thiolase (patient, 3.9 nmol/min/mg protein; controls (n = 6), 10.2 ± 2.3). Immunoprecipitation with antibodies raised against medium chain 3-ketoacyl-CoA thiolase revealed a 60% decrease compared with controls.

Very-long-chain acyl-CoA dehydrogenase subunit assembles to the dimer form on mitochondrial inner membrane

This paper describes the process of dimer assembly of mitochondrial very‐long‐chain acyl‐CoA dehydrogenase (VLCAD) subunit. Mature VLCAD is a homodimer of a 70‐kDa protein associated with the mitochondrial membrane. Newly synthesized VLCAD was present as a monomer and the major fraction was associated with the mitochondrial inner membrane. The association of VLCAD subunit with the mitochondrial membrane was observed early during dimer formation. In contrast, a VLCAD monomeric mutant S583W, a novel mutation identified from a patient with VLCAD deficiency, did not associate with the mitochondrial membrane after import and the major fraction remained in the mitochondrial matrix. These results suggest that association of VLCAD protein with mitochondrial inner membrane is necessary for dimer assembly and formation of mature VLCAD.

Purification and characterization of two isoforms of chlorogenic acid oxidase from sweet potato cells in suspension culture

Summary Two isoforms (PPO-E and PPO-A) of chlorogenic acid oxidase (CAO) were purified from sweet potato ( Ipomoea batatas ) cells in suspension culture and characterized. The isoforms were separated by chromatography on DEAE-Toyopearl and Butyl-Toyopearl. The molecular masses of PPO-E and PPO-A were estimated to be 40 Ku and 39 Ku, respectively, by SDS-polyacrylamide gel electrophoresis. The isoforms had a different optimal pH and a different Km for chlorogenic acid from one another. In addition, 60-Ku polypeptides, which had polyphenol oxidase (PPO) activity reacted with antibodies against PPO-E and against PPO-A in immunoblotting analysis. The amino-terminal amino acid sequences of PPO-E and PPO-A were rather similar and resembled those of 60-Ku PPOs isolated from other plants. These results suggest that PPO-E and PPO-A were isoforms of PPO in the cultured cells of sweet potato and that they might be generated by carboxy-terminal processing of 60-Ku forms of PPO in vivo .