Molecular cloning of cDNA encoding mitochondrial very-long-chain acyl-CoA dehydrogenase from bovine heart.
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AIM: To clone the cDNA encoding an isoenzyme of mitochondrial very-long-chain acyl-CoA dehydrogenase (VLCAD) from bovine heart lambda gt11 and lambda gt10 cDNA libraries. METHODS: The clone was isolated with immunoscreening technique and validated by (1) the microsequences of the N-terminus and three internal proteolytic fragments from the purified enzyme; (2) identification of the acyl-CoA dehydrogenase (AD) signature sequence; and (3) high homology of the deduced peptide sequences, as expected, with those of rat liver mitochondrial VLCAD. RESULTS: The cDNA (2203 bp) corresponds to a approximately 2.4-kb mRNA band from the same tissue source revealed by a Northern blotting. The deduced peptide sequence of 655 amino acids (70,537 Da) is composed of a 40-amino acid mitochondrial leader peptide moiety (4,346 Da) and a 615-amino acid peptide as a mature protein (66,191 Da). A comparison of the peptide sequences in the AD family shows the major diversity in their signal sequences, suggesting a structural basis for their different mitochondrial locations. The catalytic sites are all highly conserved among VLCAD. Ser-251 analogous to and Cys-215 diversified to other family members. A pseudo-consensus sequence of leucine zipper was found in the C-terminal region from Leu-568 to Leu-589, implying a mechanism whereby the dimer of this protein is formed by zipping these leucine residues from the alpha-helixes of 2 monomers. CONCLUSION: The isolated cDNA clone encodes an isoenzyme of mitochondrial VLCAD in bovine heart. (+info)
The medium-/long-chain fatty acyl-CoA dehydrogenase (fadF) gene of Salmonella typhimurium is a phase 1 starvation-stress response (SSR) locus.
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Salmonella enterica serovar Typhimurium (S. typhimurium) is an enteric pathogen that causes significant morbidity in humans and other mammals. During their life cycle, salmonellae must survive frequent exposures to a variety of environmental stresses, e.g. carbon-source (C) starvation. The starvation-stress response (SSR) of S. typhimurium encompasses the genetic and physiological realignments that occur when an essential nutrient becomes limiting for bacterial growth. The function of the SSR is to produce a cell capable of surviving long-term starvation. This paper reports that three C-starvation-inducible lac fusions from an S. typhimurium C-starvation-inducible lac fusion library are all within a gene identified as fadF, which encodes an acyl-CoA dehydrogenase (ACDH) specific for medium-/long-chain fatty acids. This identification is supported by several findings: (a) significant homology at the amino acid sequence level with the ACDH enzymes from other bacteria and eukaryotes, (b) undetectable beta-oxidation levels in fadF insertion mutants, (c) inability of fad insertion mutants to grow on oleate or decanoate as a sole C-source, and (d) inducibility of fadF::lac fusions by the long-chain fatty acid oleate. In addition, the results indicate that the C-starvation-induction of fadF is under negative control by the FadR global regulator and positive control by the cAMP:cAMP receptor protein complex and ppGpp. It is also shown that the fadF locus is important for C-starvation-survival in S. typhimurium. Furthermore, the results demonstrate that fadF is induced within cultured Madin-Darby canine kidney (MDCK) epithelial cells, suggesting that signals for its induction (C-starvation and/or long-chain fatty acids) may be present in the intracellular environment encountered by S. typhimurium. However, fadF insertion mutations did not have an overt effect on mouse virulence. (+info)
Oxidation of medium-chain acyl-CoA esters by extracts of Aspergillus niger: enzymology and characterization of intermediates by HPLC.
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The activities of beta-oxidation enzymes were measured in extracts of glucose- and triolein-grown cells of Aspergillus niger. Growth on triolein stimulated increased enzyme activity, especially for acyl-CoA dehydrogenase. No acyl-CoA oxidase activity was detected. HPLC analysis after incubation of triolein-grown cell extracts with decanoyl-CoA showed that beta-oxidation was limited to one cycle. Octanoyl-CoA accumulated as the decanoyl-CoA was oxidized. Beta-oxidation enzymes in isolated mitochondrial fractions were also studied. The results are discussed in the context of methyl ketone production by fungi. (+info)
Outcome of medium chain acyl-CoA dehydrogenase deficiency after diagnosis.
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BACKGROUND: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common inborn error of fatty acid metabolism. Undiagnosed, it has a mortality rate of 20-25%. Neonatal screening for the disorder is now possible but it is not known whether this would alter the prognosis. OBJECTIVE: To investigate the outcome of MCAD deficiency after the diagnosis has been established. METHOD: All patients with a proved diagnosis of MCAD deficiency attending one centre in a four year period were reviewed. RESULTS: Forty one patients were identified. Follow up was for a median of 6.7 years (range, 9 months to 14 years). Nearly half of the patients were admitted to hospital with symptoms characteristic of MCAD deficiency before the correct diagnosis was made. After diagnosis, two patients were admitted to hospital with severe encephalopathy but there were no additional deaths or appreciable morbidity. There was a high incidence (about one fifth) of previous sibling deaths among the cohort. CONCLUSIONS: Undiagnosed, MCAD deficiency results in considerable mortality and morbidity. However, current management improves outcome, supporting the view that the disorder should be included in newborn screening programmes. (+info)
A novel acyl-CoA oxidase that can oxidize short-chain acyl-CoA in plant peroxisomes.
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Short-chain acyl-CoA oxidases are beta-oxidation enzymes that are active on short-chain acyl-CoAs and that appear to be present in higher plant peroxisomes and absent in mammalian peroxisomes. Therefore, plant peroxisomes are capable of performing complete beta-oxidation of acyl-CoA chains, whereas mammalian peroxisomes can perform beta-oxidation of only those acyl-CoA chains that are larger than octanoyl-CoA (C8). In this report, we have shown that a novel acyl-CoA oxidase can oxidize short-chain acyl-CoA in plant peroxisomes. A peroxisomal short-chain acyl-CoA oxidase from Arabidopsis was purified following the expression of the Arabidopsis cDNA in a baculovirus expression system. The purified enzyme was active on butyryl-CoA (C4), hexanoyl-CoA (C6), and octanoyl-CoA (C8). Cell fractionation and immunocytochemical analysis revealed that the short-chain acyl-CoA oxidase is localized in peroxisomes. The expression pattern of the short-chain acyl-CoA oxidase was similar to that of peroxisomal 3-ketoacyl-CoA thiolase, a marker enzyme of fatty acid beta-oxidation, during post-germinative growth. Although the molecular structure and amino acid sequence of the enzyme are similar to those of mammalian mitochondrial acyl-CoA dehydrogenase, the purified enzyme has no activity as acyl-CoA dehydrogenase. These results indicate that the short-chain acyl-CoA oxidases function in fatty acid beta-oxidation in plant peroxisomes, and that by the cooperative action of long- and short-chain acyl-CoA oxidases, plant peroxisomes are capable of performing the complete beta-oxidation of acyl-CoA. (+info)
Cloning and mapping of three pig acyl-CoA dehydrogenase genes.
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To investigate the structure of porcine genes involved in the beta-oxidation of fatty acid, we isolated the short-chain acyl-CoA dehydrogenase (SCAD), medium-chain acyl-CoA dehydrogenase (MCAD), and long-chain acyl-CoA dehydrogenase (LCAD) genes from the pig. The cDNA of SCAD, MCAD and LCAD genes were 1899 bp, 1835 bp 1835 bp and 1704 bp long and coded for 413-aa, 422-aa and 430-aa precursor proteins, respectively. Three genes, SCAD, MCAD and LCAD were mapped to 14p16.2-23.2, 6q32.4-33, and 15q24.2-26.3, respectively. (+info)
Peroxisome proliferator-activated receptor alpha mediates the adaptive response to fasting.
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Prolonged deprivation of food induces dramatic changes in mammalian metabolism, including the release of large amounts of fatty acids from the adipose tissue, followed by their oxidation in the liver. The nuclear receptor known as peroxisome proliferator-activated receptor alpha (PPARalpha) was found to play a role in regulating mitochondrial and peroxisomal fatty acid oxidation, suggesting that PPARalpha may be involved in the transcriptional response to fasting. To investigate this possibility, PPARalpha-null mice were subjected to a high fat diet or to fasting, and their responses were compared with those of wild-type mice. PPARalpha-null mice chronically fed a high fat diet showed a massive accumulation of lipid in their livers. A similar phenotype was noted in PPARalpha-null mice fasted for 24 hours, who also displayed severe hypoglycemia, hypoketonemia, hypothermia, and elevated plasma free fatty acid levels, indicating a dramatic inhibition of fatty acid uptake and oxidation. It is shown that to accommodate the increased requirement for hepatic fatty acid oxidation, PPARalpha mRNA is induced during fasting in wild-type mice. The data indicate that PPARalpha plays a pivotal role in the management of energy stores during fasting. By modulating gene expression, PPARalpha stimulates hepatic fatty acid oxidation to supply substrates that can be metabolized by other tissues. (+info)
Evaluating newborn screening programmes based on dried blood spots: future challenges.
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A UK national programme to screen all newborn infants for phenylketonuria was introduced in 1969, followed in 1981 by a similar programme for congenital hypothyroidism. Decisions to start these national programmes were informed by evidence from observational studies rather than randomised controlled trials. Subsequently, outcome for affected children has been assessed through national disease registers, from which inferences about the effectiveness of screening have been made. Both programmes are based on a single blood specimen, collected from each infant at the end of the first week of life, and stored as dried spots on a filter paper or 'Guthrie' card. This infrastructure has made it relatively easy for routine screening for other conditions to be introduced at a district or regional level, resulting in inconsistent policies and inequitable access to effective screening services. This variation in screening practices reflects uncertainty and the lack of a national framework to guide the introduction and evaluation of new screening initiatives, rather than geographical variations in disease prevalence or severity. More recently, developments in tandem mass spectrometry have made it technically possible to screen for several inborn errors of metabolism in a single analytical step. However, for each of these conditions, evidence is required that the benefits of screening outweigh the harms. How should that evidence be obtained? Ideally policy decisions about new screening initiatives should be informed by evidence from randomised controlled trials but for most of the conditions for which newborn screening is proposed, large trials would be needed. Prioritising which conditions should be formally evaluated, and developing a framework to support their evaluation, poses an important challenge to the public health, clinical and scientific community. In this chapter, issues underlying the evaluation of newborn screening programmes will be discussed in relation to medium chain acyl CoA dehydrogenase deficiency, a recessively inherited disorder of fatty acid oxidation. (+info)