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Coding sequence mutations in the alpha subunit of propionyl-CoA carboxylase in patients with propionic acidemia.

Propionic acidemia is a rare autosomal recessive disorder of intermediary metabolism. It is caused by a deficiency of the mitochondrial enzyme propionyl-CoA carboxylase (PCC, EC 6.4.1.3), a heteropolymeric protein composed of two subunits, alpha and beta. PCC requires ATP and biotin as cofactors for the reaction, the latter enzymatically added onto the alpha subunit. We investigated coding sequence mutations in the alpha subunit of PCC by analyzing fibroblast RNA from propionic acidemia patients deficient in alpha subunit function by single-strand conformation polymorphism and direct sequencing. Five missense mutations and one short in-frame deletion were found among different patients. Four mutations were located in the putative biotin carboxylase domain, whereas the two others were within the 67-amino-acid C-terminal domain previously shown to be required to obtain biotinylation of the alpha subunit. We analyzed fibroblast extracts for the presence of a biotinylated alpha subunit by Western blot analysis using streptavidin coupled to alkaline phosphatase. Four of five cell lines failed to show a biotinylated alpha subunit, regardless of the position of the mutations within the coding sequence. Two mutations located in the biotinylation domain were expressed in an Escherichia coli-based system and shown to abolish biotinylation of the domain. The results suggest that most mutations have a severe impact on the stability or the functionality of the alpha subunit.

Alkaline Phosphatase↗

Inhibition of growth by imidazol(on)e propionic acid: evidence in vivo for coordination of histidine catabolism with the catabolism of other amino acids.

Imidazole propionic acid (ipa), a gratuitous inducer of the histidine-utilization (hut) system in Salmonella typhimurium, inhibits the organism's growth on succinate minimal medium. Induction of the hut system is necessary, but not sufficient, to cause inhibition. A study of the ability of single amino acids to relieve ipa-restricted growth suggests that insufficient glutamate is the cause of slow growth. The inhibition of growth by imidazolone propionic acid (iopa), an intermediate in the catabolism of histidine to glutamate, is similar to that by ipa. Studies using 2, 3, 5-triphenyl tetrazolium chloride plates to examine amino acid catabolism suggest that accumulation of ipa or iopa leads to inactivation of aspartate amino-transferase (AAT). This interpretation is supported by studies of an Escherichia coli mutant lacking AAT. The mutant grows poorly on succinate minimal medium, and the poor growth is relieved by the same amino acids that relieve ipa- and iopa-restricted growth. These and other findings are discussed in terms of coordination of the histidine-utilization system with enzymatic activities involved in the catabolism of other amino acids.

Amino Acid Oxidoreductases↗

Spore activation by acetate, propionate and heat in Phycomyces mutants.

Exposure to heat, acetate, or propionate activates the spores of the fungus Phycomyces blakesleeanus and allows them to germinate. Using counterselection with the antibiotic N-glycosyl-polyfungin, seven mutants were isolated on the basis of decreased spore activation by propionate. The nine mutants showed decreased activation by both chemicals and by heat, increased heat lethality, and altered patterns of trehalase activation. These and other observations indicate that spore activation by the three agents and spore death by heat are mediated by the same cellular component(s), which is probably involved in the regulation of cyclic AMP concentration.

Acetates↗

Excretion of 2-methyl-3-oxovaleric acid in propionic acidemia.

A new case of propionic acidemia is presented, paying special attention to the early symptoms of this disease, such as increased drowsiness, muscular hypotonia, poor feeding, hypothermia, metabolic acidosis, ketonuria and vomiting. Investigation by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) revealed the excretion of fairly high amounts of 2-methyl-3-oxovaleric acid, a condensation product of two molecules of propionyl-CoA, as well as the known pathological metabolites such as propionic, 3-hydroxypropionic and methylcitric acids. Among the post mortem findings the histological studies of the liver were the most remarkable.

Acidosis↗

The molecular defect in propionic acidemia: exon skipping caused by an 8-bp deletion from an intron in the PCCB allele.

Propionic acidemia is an autosomal recessive metabolic disease resulting from a deficiency of propionyl CoA carboxylase (PCC) activity. To investigate the genetic basis of propionic acidemia, we isolated a cDNA encoding the precursor of the beta subunit of human PCC (beta PCC). The cloned cDNA sequence was 1,832 bp long and the open reading frame of 1,617 nucleotides encoded a polypeptide of 539 amino acids with a molecular mass of 58,202 Da. The human beta PCC sequence shared a high degree of homology (91%) with the full-length cDNA of rat beta PCC at the amino acid level; there were only 47 differences among 539 amino acid residues compared. Polymerase chain reaction amplification and sequencing of cDNA from a beta subunit-deficient Japanese patient revealed a deletion of 101 nucleotides consisting of one exon from mature mRNA. This deletion resulted in a frameshift and a stop codon in the new frame. Analysis of the genomic DNA revealed a homozygous 8-bp deletion from bp3 to bp10 of the intron just downstream of the deleted exon. This deletion disrupted the consensus 5' splice signal and led to exon skipping.

Alleles↗

Plasma total odd-chain fatty acids in the monitoring of disorders of propionate, methylmalonate and biotin metabolism.

Total plasma odd-numbered long-chain fatty acids were analysed in patients with methylmalonic acidaemia (vitamin B12-responsive and unresponsive), combined methylmalonic acidaemia/homocystinuria (CblC), propionic acidaemia (both neonatal-onset and late-onset), biotinidase deficiency and holocarboxylase synthase deficiency, as well as in hospital controls. Total odd-numbered long-chain fatty acids (C15:0, C17:1 and C17:0) were expressed as a percentage of total C12-C20 fatty acids. Control values were 0.72% +/- 0.31% (n = 12). Normalization of the percentage of odd-chain fatty acids occurred in all vitamin-responsive patients, following the institution of vitamin treatment. In general the neonatal-onset propionic acidaemia and B12-unresponsive methylmalonic acidaemia patients had the highest plasma odd-chain fatty acid concentrations, which correlated with the clinical condition but not with the urinary excretion of methylcitrate or methylmalonate. Plasma odd-chain fatty acid concentrations and methylmalonate excretions in CblC patients reacted very well to vitamin B12 treatment, but with no clinical response. Measurement of plasma odd-chain fatty acids is of no value for the monitoring of defects of biotin metabolism.

Adolescent↗

Clinical outcome and long-term management of 17 patients with propionic acidaemia.

UNLABELLED: A retrospective study was performed on the clinical outcome and long-term treatment of 17 patients with propionic acidaemia diagnosed during the last 20 years in our hospital. The study group consisted of 12 patients with early onset type of disease and 5 patients with late onset. Seven (41%) patients died, five with early onset and two with late onset. The deceased early onset patients had a median survival of 0.4 years while the deceased late onset patients died at the age of 2.8 and 4 years respectively. Median age of the living early onset patients was 5.2 (1-9.25) years, the late onset patients were 4, 7 and 23 years old. Patients were all treated with natural protein restriction and in most cases carnitine and metronidazole were added. The early onset patients were almost all treated with daily home tube feeding. The mean natural protein intake of early onset patients (6.3 +/- 1.5 g/day) was significantly lower than the natural protein intake of late onset patients (17.6 +/- 5.3 g/day). Supplemental protein intake was higher in early onset patients. The general neurological outcome of our study group was satisfactory with a better outcome for early onset patients. As to growth, many patients showed a failure to thrive, this was particularly for height. The strong protein restriction during the first years of life probably contributed to this. CONCLUSION: The prognosis for patients with propionic acidaemia appeared to be satisfactory in terms of survival and outcome characteristics such as neurological and mental development. Despite these results the authors feel that the prognosis and quality of life of these patients might be improved with liver transplantation or possibly somatic gene therapy in the future.

Adolescent↗

Cardiomyopathy in propionic acidaemia.

Following the death of a patient with propionic acidaemia with a cardiomyopathy we reviewed 19 patients with the same disorder for evidence of cardiomyopathy. Six patients were found to meet the diagnostic criteria. Three patients died and in the other three the cardiac disease resolved completely. All patients were treated with standard therapy and some received L-carnitine but this did not seem to influence the eventual outcome. Cardiomyopathy is an important complication of propionic acidaemia and may be rapidly fatal.

Amino Acid Metabolism, Inborn Errors↗

Effects of adenosine on neutrophil polarization induced by N-formyl-methionyl-leucyl-phenylalanine, sodium propionate and colchicine.

Polarization of human neutrophils (a characteristic bipolar shape change) can be induced by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP); sodium propionate, which causes a rapid acidification of the cytosol; or colchicine, which disrupts microtubules. We have previously reported that adenosine, endogenously produced in human neutrophil suspensions, inhibits FMLP-induced polarization. We report here that endogenously produced adenosine also inhibits sodium propionate-induced polarization but has no effect on colchicine-induced polarization. These results suggest that neutrophil polarization may be a multistep process inducible by compounds that trigger different biochemical events.

Adenosine↗

Acute infantile hemiplegia in a patient with propionic acidaemia.

A 10-month-old girl with mild developmental delay became hemiplegic after seizures. Cranial CT scan and magnetic resonance imaging (MRI) revealed no lesions related to vascular diseases, but brain atrophy on the right side was remarkable. Digital subtraction angiography showed slightly decreased visualization of peripheral branches of the right medial cerebral artery. Propionic acidaemia was diagnosed on the basis of high plasma levels of propionic acid and its metabolites and the elevated urinary excretion of these acids. With therapy, the levels of these acids fell, and her left hemiplegia disappeared 3 months later.

Amino Acid Metabolism, Inborn Errors↗

Late onset type of propionic acidaemia: case report and biochemical studies.

A late-onset case of propionic acidaemia with favourable response to restriction of dietary protein is described. During a keto-acidotic crisis, this patient demonstrated unexpectedly low concentrations of propionic acid and glycine in blood and urine but increased urinary output of some secondary metabolites.

Acidosis↗

Interactive effects of propionic acid and temperature on growth and ochratoxin a production by Penicillium aurantiogriseum.

Propionate at concentrations up to 0.05% decreased at 25 degrees C the growth and sporulation of Penicillium aurantiogriseum. The standard size of conidiogenous structures (metulae, phialids) and conidia was diminished. The effect was more pronounced at a higher temperature (30 degrees C). Inhibition of ochratoxin production by propionate was also demonstrated.

Ochratoxins↗

Liver transplantation in propionic acidaemia.

Despite the improvement in dietary therapy during the past 20 years, the overall outcome of severe forms of propionic acidaemia (PA) remains often disappointing. Good results can be obtained at a very high price in terms of medical attention, family burden and high cost. In most early onset forms of PA, the intake of natural protein must be rigidly restricted to 8-12 g/day for the first 3 years of life, and then slowly increased to 15-20 g/day by the age of 6-8 years. Supplementation with a precursor-free aminoacid mixture to provide 1.5 g/kg protein per day is generally recommended, although remains controversial. From the age of 1 year onward, these children are often severely anorectic and most of the diet must be delivered by nocturnal gastric drip feeding or gastrostomy. Metronidazole is very effective in reducing the excretion of propionate metabolites derived from the gut. L-carnitine (50 to 100 mg/kg) is systematically given to promote propionylcarnitine synthesis and excretion. We report here a retrospective study of 33 patients with PA diagnosed during the last 20 years in our hospital. Of them, 2 have been liver transplanted. In these two patients who presented frequent severe and unexpected metabolic decompensations despite good compliance with the dietary therapy, orthotopic liver transplantation (OLT) was done at 7 and 9 years respectively. One child died 15 months after transplantation due to a severe lymphoproliferative disorder; the other child now aged 13.5 years is doing well. Despite a persistent methylcitrate excretion, she is under normal moderate daily protein intake (40-50 g/day) and still on carnitine supplementation. Interestingly, another patient who filled the criteria for OLT (very frequent and severe decompensations leading to frequent admissions to the intensive care unit despite excellent dietary management) was also placed on the list for OLT. From the time he was registered onward, he experienced no further episodes of metabolic decompensation, there was almost no interruption in his daily intake and he gained height and weight and developed well. He was finally removed from the list and is still doing very well 2 years thereafter. Correction of propionylCoA carboxylase deficiency restricted to hepatic tissues seems to induce a change towards clinical normalisation and a milder biochemical phenotype. Liver transplanted PA patients still require slight protein restriction and carnitine treatment. We consider that at the moment OLT should only be performed in severe forms of PA, mostly characterised by frequent and unexpected episodes of metabolic decompensation despite good dietary therapy. However, a strict appreciation of these criteria is difficult. A more generalised indication for OLT in PA will require more information about the long-term outcome of transplanted patients. We should also await other alternatives like auxiliary partial OLT from living donors or transplantation of isolated allogenic hepatocytes, genetically modified or not.

Adolescent↗

An on-line technique for monitoring propionic acid fermentation.

An on-line technique, based on measuring the increase in pressure due to CO(2) release in a closed air-tight reactor, was used to evaluate the fermentation of lactate by propionibacteria. The method was applied to batch cultures of Propionibacterium shermanii grown in yeast extract/sodium lactate medium containing lactate as a carbon source under micro-aerophilic conditions. Gas pressure evolution was compared both with substrate consumption and metabolites production and with acidification and growth. Linear relationships were found between gas pressure variation, lactate consumption and propionate and acetate production. The technique also enabled the evaluation of total CO(2) produced, by taking account of pressure, oxygen and pH measurements. These results tend to show that this simple and rapid method could be useful to monitor propionic acid bacteria growth.

Acetates↗

Propionic acid production in an in situ cell retention bioreactor.

Continuous fermentations were conducted with in situ cell retention using spin filters (pore size 5 microm and 10 microm) for propionic acid production by Propionibacterium acidipropionici. Continuous fermentation with a 5-microm pore size spin filter resulted in 50% cell retention. Propionic acid productivity was enhanced (0.9 g l(-1) h(-1)) by approximately four-fold compared to conventional batch fermentation (0.25 g l(-1) h(-1)). The in situ cell retention (5-microm pore size spin filter) bioreactor was operated continuously and smoothly for 8 days at a dilution rate of D=0.05 h(-1).

Bioreactors↗

Unexpectedly high prevalence of the mild form of propionic acidemia in Japan: presence of a common mutation and possible clinical implications.

Propionic acidemia [MIM 606054] is a form of organic acidemia caused by genetic deficiency of propionyl-CoA carboxylase (PCC) and characterized by attacks of severe metabolic acidemia and hyperammonemia beginning in the neonatal period or in early infancy. There are, however, patients who have higher PCC activities and present later with unusual symptoms, such as mild mental retardation or extrapyramidal symptoms, sometimes even without metabolic acidosis. Through the neonatal screening of more than 130,000 Japanese newborns we detected a frequency of patients with propionic acidemia more than ten times higher than previously reported, most of them with milder phenotypes. The mutational spectrum was quite different from that of patients with the severe form and there was a common mutation (Y435C) in the beta subunit of the PCC gene (PCCB). Since patients with the mild form could present with unusual symptoms and therefore could easily remain unrecognized, it is important to identify those patients and clarify their natural history. Molecularly, one of the mutations (A1288C) caused an unusual pattern of multiple exon skipping and another unidentified mutation lead to the absence of mRNA. Taking into consideration previous findings regarding PCCB mutations, it appears that this gene is particularly prone to posttranscriptional modifications such as missense mediated exon skipping, mRNA decay, or rapid product degradation.

Adolescent↗

The regulation of hepatic gluconeogenesis using alpha-ketoisovalerate and propionate as precursors.

The regulation of gluconeogenesis from alpha-ketoisovalerate and propionate was investigated in perfused livers from fasted rats. With alpha-ketoisovalerate as the gluconeogenic precursor, infusion of beta-hydroxybutyrate and acetate stimulated the rate of alpha-ketoisovalerate decarboxylation, but inhibited the rate of glucose production. Oleate, on the other hand, inhibited both alpha-ketoisovalerate decarboxylation and glucose production. When propionate was the primary gluconeogenic substrate, oleate, beta-hydroxybutyrate, and acetate infusion did not significantly alter hepatic glucose production. The present studies suggest that gluconeogenesis from alpha-ketoisovalerate is regulated at the level of various dehydrogenases prior to formation of propionyl-CoA, but subsequent to the branched-chain alpha-keto acid dehydrogenase reaction.

3-Hydroxybutyric Acid↗