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Results for “LIPOAMIDE DEHYDROGENASE”

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PubMed1981

Further studies of sulfoxide-reducing enzyme system.

Various kinds of flavoenzymes such as NADPH-cytochrome c reductase, NADH-cytochrome b5 reductase, xanthine oxidase, lipoamide dehydrogenase and NADH dehydrogenase supplemented with their electron donors exhibited the sulfoxide reductase activity in the presence of a partially purified soluble factor from guinea pig liver. The present study suggests that new electron transfer systems in which the soluble factor functions as an electron carrier coupled with flavoenzymes described above are responsible for the sulfoxide reduction.

Animals↗
PubMed2004

Protein thiol modifications visualized in vivo.

Thiol-disulfide interconversions play a crucial role in the chemistry of biological systems. They participate in the major systems that control the cellular redox potential and prevent oxidative damage. In addition, thiol-disulfide exchange reactions serve as molecular switches in a growing number of redox-regulated proteins. We developed a differential thiol-trapping technique combined with two-dimensional gel analysis, which in combination with genetic studies, allowed us to obtain a snapshot of the in vivo thiol status of cellular proteins. We determined the redox potential of protein thiols in vivo, identified and dissected the in vivo substrate proteins of the major cellular thiol-disulfide oxidoreductases, and discovered proteins that undergo thiol modifications during oxidative stress. Under normal growth conditions most cytosolic proteins had reduced cysteines, confirming existing dogmas. Among the few partly oxidized cytosolic proteins that we detected were proteins that are known to form disulfide bond intermediates transiently during their catalytic cycle (e.g., dihydrolipoyl transacetylase and lipoamide dehydrogenase). Most proteins with highly oxidized thiols were periplasmic proteins and were found to be in vivo substrates of the disulfide-bond-forming protein DsbA. We discovered a substantial number of redox-sensitive cytoplasmic proteins, whose thiol groups were significantly oxidized in strains lacking thioredoxin A. These included detoxifying enzymes as well as many metabolic enzymes with active-site cysteines that were not known to be substrates for thioredoxin. H(2)O(2)-induced oxidative stress resulted in the specific oxidation of thiols of proteins involved in detoxification of H(2)O(2) and of enzymes of cofactor and amino acid biosynthesis pathways such as thiolperoxidase, GTP-cyclohydrolase I, and the cobalamin-independent methionine synthase MetE. Remarkably, a number of these proteins were previously or are now shown to be redox regulated.

Binding Sites↗
PubMed1999

Preformulation study of the vaccine candidate P64k against Neisseria meningitidis.

We have previously isolated, cloned and expressed in Escherichia coli the lpdA gene coding for a high-molecular-mass protein (P64k) common to many meningococcal strains. P64k is an outer membrane lipoamide dehydrogenase that is highly immunogenic in animals. Here we describe a preformulation study of the recombinant protein as a vaccine candidate against Neisseria meningitidis, in which six variants containing the candidate were tested. Three assays were used to identify the most suitable variant for further evaluation: percentage of adsorption, identification of P64k by SDS/PAGE, and immunogenicity in mice. All the preformulation variants studied showed more than 98% of adsorption of P64k on the aluminium gel. After desorption, P64k was also identified by SDS/PAGE in the six preformulation variants. Seroconversion was attained in all groups analysed. On the basis of these results, the most effective variant consisted of 20 microg/ml P64k plus 0.5 mg/ml aluminium hydroxide.

Adjuvants, Immunologic↗
PubMed2000

Dehydroascorbic acid uptake in a human keratinocyte cell line (HaCaT) is glutathione-independent.

Vitamin C plays an important role in neutralizing toxic free radicals formed during oxidative metabolism or UV exposure of human skin. This study was performed to investigate the mechanisms that regulate the homoeostasis of vitamin C in HaCaT cells by identifying the events involved in the transport and in the reduction of dehydroascorbic acid. Dehydroascorbic acid accumulated to a greater extent and faster compared with ascorbic acid; its transport appeared to be mediated by hexose transporters and was entirely distinct from ascorbic acid transport. Dehydroascorbate reductase activity was unaffected by glutathione depletion, although it was sensitive to thiol protein reagents. These observations, as well as the subcellular distribution of this enzymic activity and the cofactor specificity, indicate that thioredoxin reductase and lipoamide dehydrogenase play an important role in this reduction process. HaCaT cells were able to enhance their dehydroascorbic acid reductase activity in response to oxidative stress.

Ascorbic Acid↗
PubMed1975

The sequence of amino acid residues around the oxidation-reduction active disulfide in yeast glutathione reductase.

A 14-residue peptide containing the oxidation-reduction active cystine residue from yeast glutathione reductase has been isolated from proteolytic digests of the enzyme in which the free sulfhydryl groups had been reacted with N-ethylmaleimide. The sequence of this disulfide-containing peptide was found to be:(see article). The sequence was highly homologous with the active cystine regions in Escherichia coli and pig heart lipoamide dehydrogenase. The sequences of three of the postulated four thiol-containing regions of the enzyme are also presented, as well as evidence supporting the view that the enzyme is composed of two identical subunits.

Amino Acid Sequence↗
PubMed2001

[Mitochondrial DNA T to G mutation 8993 in Leigh encephalopathy and organic aciduria].

We report a 10-month-old female infant with Leigh encephalopathy caused by a T to G mutation at nucleotide 8993 of mitochondrial DNA. Initial manifestations were diarrhea and pyrexia, followed by disturbance of consciousness. Blood chemistry showed lactic acidosis, and cranial T2 weighted magnetic resonance imaging demonstrated symmetric high-intensity areas in the basal ganglia, consistent with Leigh encephalopathy. Analysis of urinary organic acids revealed a increase of alpha-ketoglutamate. Derivatives of branched chain amino acids, which accumulate in maple syrup disease, were also increased. Lipoamide dehydrogenase (E3) deficiency was initially suspected; however, normal activity of pyruvate dehydrogenase complex excluded the diagnosis. The organic aciduria disappeared after two weeks. The CNS lesions in our case were observed more prominently in the floor of the bilateral frontal lobes than in the globus pallidus and putamen. In this case, mitochondrial DNA mutation may have caused organic aciduria and the atypical imaging findings.

DNA, Mitochondrial↗