Assignment of electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) to human chromosome 4q33 by fluorescence in situ hybridization and somatic cell hybridization.

Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is a nuclear-encoded protein located in the inner mitochondrial membrane. Inherited defects of ETF-QO cause glutaric acidemia type II. We here describe the localization of the ETF-QO gene to human chromosome 4q33 by somatic cell hybridization and fluorescence in situ hybridization.

Molecular cloning and expression of a cDNA encoding human electron transfer flavoprotein-ubiquinone oxidoreductase.

Electron-transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) in the inner mitochondrial membrane accepts electrons from electron-transfer flavoprotein which is located in the mitochondrial matrix and reduces ubiquinone in the mitochondrial membrane. The two redox centers in the protein, FAD and a [4Fe4S]+2,+1 cluster, are present in a 64-kDa monomer. We cloned several cDNA sequences encoding the majority of porcine ETF-QO and used these as probes to clone a full-length human ETF-QO cDNA. The deduced human ETF-QO sequence predicts a protein containing 617 amino acids (67 kDa), two domains associated with the binding of the AMP moiety of the FAD prosthetic group, two membrane helices and a motif containing four cysteine residues that is frequently associated with the liganding of ferredoxin-like iron-sulfur clusters. A cleavable 33-amino-acid sequence is also predicted at the amino terminus of the 67-kDa protein which targets the protein to mitochondria. In vitro transcription and translation yielded a 67-kDa immunoprecipitable product as predicted from the open reading frame of the cDNA. The human cDNA was expressed in Saccharomyces cerevisiae, which does not normally synthesize the protein. The ETF-QO is synthesized as a 67-kDa precursor which is targeted to mitochondria and processed in a single step to a 64-kDa mature form located in the mitochondrial membrane. The detergent-solubilized protein transfers electrons from ETF to the ubiquinone homolog, Q1, indicating that both the FAD and iron-sulfur cluster are properly inserted into the heterologously expressed protein.

Medium-chain acyl-CoA dehydrogenase deficiency: metabolic effects and therapeutic efficacy of long-term L-carnitine supplementation.

Medium-chain acyl-CoA dehydrogenase deficiency is a recently described inborn error of metabolism characterized by episodes of coma and hypoketotic hypoglycaemia in response to prolonged fasting. Secondary carnitine deficiency has been documented in these patients as well as the excretion in the urine of medium-chain-length acyl carnitine esters, such as octanoylcarnitine. Based on the potential toxicity of medium-chain fatty acid metabolites and the beneficial responses of patients with other inborn errors of metabolism and secondary carnitine deficiency, oral carnitine has been proposed as treatment for children with medium-chain acyl-CoA dehydrogenase deficiency. We report the results of carefully monitored fasting challenges of an infant with this deficiency both before and after 3 months of oral carnitine therapy. Carnitine supplementation failed to prevent lethargy, vomiting, hypoglycaemia and accumulation of free fatty acids in response to fasting despite normalization of plasma carnitine levels and a marked increase in urinary excretion of acyl-carnitine esters. Potentially toxic medium-chain fatty acids accumulated in the plasma in spite of therapy. Based on this study of one patient, we stress that avoidance of fasting and prompt institution of glucose supplementation in situations when oral intake is interrupted remain the mainstays of therapy for medium-chain acyl-CoA dehydrogenase deficient patients.

Serotonin and 5-hydroxyindoleacetic acid in brains of suicide victims. Comparison in chronic schizophrenic patients with suicide as cause of death.

Serotonin (5-HT) and 5-hydroxyindoleacetic acid concentrations were determined in various brain areas of nonschizophrenic suicide victims, chronic schizophrenic patients with or without suicide as the cause of death, and normal control subjects without psychiatric or neurologic disorders. Serotonin concentrations in the basal ganglia were significantly elevated in suicide victims and chronic schizophrenic patients, as were 5-hydroxyindoleacetic acid concentrations in the occipital cortex. These differences were not specific to either patient group and may have been caused by neuroleptic or antidepressant treatment. A decreased 5-HT concentration was found in the hypothalamus of nonschizophrenic suicide victims. Among the chronic schizophrenic patients, there was no significant difference in the hypothalamic 5-HT content between the suicide victims and others, indicating that low 5-HT levels in the hypothalamus are not characteristic of schizophrenic patients who died of suicide.

Biotin-responsive in vivo carboxylase deficiency in two siblings with secretory diarrhea receiving total parenteral nutrition.

Two siblings with a congenital syndrome of secretory diarrhea and seizures developed progressive skin rash, alopecia, and mucocutaneous candidiasis while receiving biotin-free total parenteral nutrition. Abnormally low urinary biotin excretion was associated with these clinical findings, but the serum concentration of biotin was within the normal range. There was also increased urinary excretion of lactic acid, 3-hydroxyisovaleric acid, 3-hydroxypropionic acid, and 3-methylcrotonylglycine. The younger of the two children subsequently died with severe metabolic acidosis. In the oder sibling, intravenous treatment with biotin (200 micrograms/day) resulted in resolution of the organic aciduria. A larger dose (10 mg/day) appeared to be required for rapid improvement in the skin lesions. These cases suggest that clinically significant biotin deficiency can occur in patients with chronic diarrhea receiving biotin-free total parenteral nutrition.