Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: KEGG:D02011 (FAD)
5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A procedure has been developed for the partial purification from Chlorella vulgaris of an enzyme which catalyzes the formation of HCN from D-histidine when supplemented with peroxidase of a metal with redox properties. Some properties of the enzyme are described. Evidence is presented that the catalytic activity for HCN formation is associated with a capacity for catalyzing the oxidation of a wide variety of D-amino acids. With D-leucine, the best substrate for O2 consumption, 1 mol of ammonia is formed for half a mol of O2 consumed in the presence of catalase. An inactive apoenzyme can be obtained by acid ammonium sulfate precipitation, and reactivated by added FAD. On the basis of these criteria, the Chlorella enzyme can be classified as a D-amino acid oxidase (EC 1.4.3.3). Kidney D-amino acid oxidase and snake venom L-amino acid oxidase, which likewise form HCN from histidine on supplementation with peroxidase, have been compared with the Chlorella D-amino acid oxidase. The capacity of these enzymes for causing HCN formation from histidine is about proportional to their ability to catalyze the oxidation of histidine.
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PMID:A D-amino acid oxidase from Chlorella vulgaris. 1 7

A general consideration of the pathogenesis of the various metabolic diseases which produce mental deficiency suggests that perturbation of the one carbon (folate) cycle may be important. Secondly, a review of diseases having some symptoms in common with trisomy 21 suggests the evidence of : a collagen disturbance (hypothyroidism and iminodipeptidurial) ; an oxygen disturbance (hypothyroidism and hemoglobinopathies) ; a cholinergic distrubance (Alzheimer's disease) ; a one-carbon-cycle disturbance (Lesch-Nyhan's disease). Thirdly, the peculiar pathology of trisomy 21 allows to find also a cholinergic disturbance and a disturbance close to the 10 formyl-tetrahydrololate entry of the folate cycle. Finally, an analysis of the possible effect of the excess of superoxide dismutase A and of the increase of glutathion peroxidase leads to the suspicion that a difficulty exists of dioxygenations and of non aromatic hydroxilations with a relative retardation of some FAD requiring reactions. A simplified scheme shows that these metabolic deviations could provoke a disturbance of the collagen and of synthesis of chemical mediators, in accordance with the indications furnished by the compared pathogenesis of the various affections studied. These heuristic reflexions open the way to further investigations.
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PMID:[Biochemical investigations and trisomy 21 (author's transl)]. 22 17

A 37-yr-old woman with nontoxic goiter is presented. The thyroid 131I uptake at 3 and 24 hr were, respectively, 77.1% and 81.4% dose. Thiocyanate discharged 65.5% of the accumulated 131I in 30 min. In vitro organification of iodine in the thyroid homogenate from the patient was impaired and it was restored to normal by the addition of H2O2, glucose, and glucose oxidase system, FAD, or reduced cytochrome b5. Riboflavin, FMN, oxidized cytochrome b5, oxidized or reduced cytochrome c, NAD(H), and NADP(H) were ineffective in the reaction. The microsomal NADH-cytochrome b5 reductase activity was definitely low in the patient's thyroid. It was augmented to a normal level by incubation of the microsomes with FAD for 30 min or more. The activities of thyroid peroxidase, G6-PD, 6-PGD, catalase, protease, and NADPH-cytochrome c reductase were within normal limits. The major thyroid protein was normal thyroglobulin which could be readily iodinated in the presence of H2O2 and horse radish peroxidase. These findings suggest the correlation of an iodide organification defect with a cytochrome b5 reductase deficiency. Administration of high doses of FAD led to the restoration of thyroidal iodide organification mechanism associated with an increased thyroid hormone production and to a marked decrease of the goiter. Riboflavin was given without effect even at a high dosage level. Consequently, it seems likely that the deficient cytochrome b5 reductase activity in this patient is due to a defect in the biosynthesis of FAD, the coenzyme of the reductase, from riboflavin.
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PMID:Deficient cytochrome b5 reductase activity in nontoxic goiter with iodide organification defect. 116 26

A simple to use, robust, quantitative, and extremely sensitive colorimetric assay for alkaline phosphatase (EC 3.1.3.1), designed to be used as a detection system in diagnostic assays employing antibodies or gene probes, is described. This technology is based on the novel principle of prosthetogenesis, according to which a purpose-designed substrate (a prosthetogen) for a primary analyte-linked enzyme label is hydrolyzed to produce a prosthetic group for a detector enzyme system. The prosthetogen employed here is a derivative of FAD which is phosphorylated at the 3'-position of the ribose ring (FADP), the label enzyme is alkaline phosphatase, and the detector is a D-amino-acid oxidase/horseradish peroxidase-coupled system. Essentially each turnover of every molecule of alkaline phosphatase produces a molecule of D-amino-acid oxidase for detection. Thus enormous amplification of the initial signal is achieved in short time periods because of the relatively high turnover number of alkaline phosphatase for FADP. The system can be formatted as a stable, preformed, freeze-dried preparation containing all analytical components, which is reconstituted simply by addition of buffer solution. This methodology can quantitate less than 0.1 amol of alkaline phosphatase in 30 min at 25 degrees C using microtiter plates.
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PMID:Amplified assay of alkaline phosphatase using flavin-adenine dinucleotide phosphate as substrate. 136 Jul 71

The gene encoding the streptococcal flavoprotein NADH oxidase (NOXase), which catalyzes the four-electron reduction of O2-->2H2O, has been cloned and sequenced from the genome of Streptococcus (Enterococcus) faecalis 10C1 (ATCC 11700). The deduced NOXase protein sequence corresponds to a molecular mass of 48.9 kDa and contains three previously sequenced cysteinyl peptides obtained with the purified enzyme. In Escherichia coli, the expressed nox gene produced a catalytically active product, which retained its immunoreactivity to affinity-purified NOXase antisera. Alignment of the NOXase protein sequence with that of streptococcal NADH peroxidase (NPXase) revealed that the proteins are 44% identical. Among the most highly conserved segments is a sequence containing Cys42; this residue is known to exist as a stabilized cysteine-sulfenic acid (Cys-SOH) in NPXase and serves as the non-flavin redox center. In addition, three previously identified NPXase segments, known to be involved in FAD and NAD(P)-binding in other pyridine nucleotide-linked flavoprotein oxidoreductases, are strongly conserved in NOXase. Overall, the extensive homology observed between NOXase and NPXase suggests that the monomer chain fold of the oxidase closely resembles that of the peroxidase. Both sequences share limited but significant homology to those of glutathione reductase and other members of the flavoprotein disulfide reductase family. These and other considerations suggest that these two unusual streptococcal flavoproteins constitute a distinct class of FAD-dependent oxidoreductases, the flavoprotein peroxide reductases, easily contrasted with enzymes such as glutathione reductase and thioredoxin reductase.
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PMID:Molecular cloning and analysis of the gene encoding the NADH oxidase from Streptococcus faecalis 10C1. Comparison with NADH peroxidase and the flavoprotein disulfide reductases. 140 82

DNA fragments encoding streptococcal NADH peroxidase (NPXase) have been amplified, cloned and sequenced from the genome of Streptococcus (Enterococcus) faecalis 10C1 (ATCC 11700). The NPXase gene (npr) comprises 1341 base-pairs and is preceded by a typical ribosome binding site. Upstream from the structural gene, putative -10 and -35 promoter regions have been identified, as has a possible factor-independent terminator that occurs in 3'-flanking sequences. The deduced relative molecular mass (Mr = 49,551), amino acid composition and isoelectric point of NPXase are in good agreement with previous values obtained with the purified enzyme. In addition, three sequenced peptides totaling approximately 20% of the protein were located in the npr gene product. From the sequencing data the deduced NPXase sequence shares low but significant homology with the flavoprotein disulfide reductase class of enzymes ranging from 21% for glutathione reductase (GRase) to 28% for thioredoxin reductase. Alignment of NPXase to Escherichia coli GRase allowed the identification of three previously reported fingerprints for the FAD, NADP+ and central domains of GRase, in the peroxidase sequence. In addition, Cys42 of NPXase, which is present as an unusual stabilized cysteine-sulfenic acid in the oxidized enzyme, aligns favorably with the charge-transfer cysteine in E. coli GRase, and both residues closely follow FAD-binding folds found near their respective amino termini. Such sequence characteristics can also be seen in mercuric reductase, lipoamide dehydrogenase and trypanothione reductase, suggesting that all these enzymes may have originally diverged from a common ancestor. Sequences that are on average 50% identical with three previously reported peptides of the related streptococcal NADH oxidase were also identified in the NPXase primary structure, suggesting a strong similarity between these flavoenzymes. Using the E. coli phage T7 expression system the npr gene has now been overexpressed in an E. coli genetic background. The resultant overexpressing clone produced a recombinant NPXase that was catalytically active and immunoreactive to NPXase antisera.
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PMID:Cloning, sequence and overexpression of NADH peroxidase from Streptococcus faecalis 10C1. Structural relationship with the flavoprotein disulfide reductases. 171 12

The apoproteins of the streptococcal NADH peroxidase (H2O2----2H2O) and NADH oxidase (O2----2H2O) stabilize the neutral forms of 6-hydroxy- and 6-mercapto-FAD, respectively. The redox behavior of the 6-hydroxy-FAD peroxidase closely mimics that of the native enzyme with both dithionite and NADH. Both oxidase and peroxidase preferentially stabilize the N(1)-protonated p-quinonoid species of 8-mercapto-FAD, and the 8-position of the bound flavin is accessible to solvent in both proteins. The 8-mercapto-FAD peroxidase yields an EH2 spectrum on reduction virtually identical to that seen with 8-mercapto-FAD glutathione reductase, but no distinct EH2.NADH form appears. The dramatic decreases in reactivity at the flavin 2- and 4-positions for both the peroxidase and the oxidase, assessed with the reconstituted 2- and 4-thio-FAD enzymes, suggest that these positions are buried by elements of both protein structures. Furthermore, reconstitution of the peroxidase with the higher potential 2- and 4-thioflavins yields enzyme forms which are fully reducible with 1.4 eq of NADH/FAD, giving rise to stable thio-FADH2.NAD+ complexes. This behavior closely mimics that of the native NADH oxidase and provides further evidence supporting the hypothesis that a major functional distinction between the two structurally related proteins is determined by the redox potential and/or NADH reactivity of the bound flavin coenzyme.
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PMID:Active-site structural comparison of streptococcal NADH peroxidase and NADH oxidase. Reconstitution with artificial flavins. 174 Apr 31

A highly sensitive flavin adenine dinucleotide-3'-phosphate (FADP)-based enzyme amplification cascade has been developed for determining alkaline phosphatase (ALP; EC 3.1.3.1). The cascade detects ALP via the dephosphorylation of the novel substrate FADP to produce the cofactor FAD, which binds stoichiometrically to inactive apo D-amino acid oxidase (D-AAO). The resulting active holo D-AAO oxidizes D-proline to produce hydrogen peroxide, which is quantified by the horseradish peroxidase-mediated conversion of 3,5-dichloro-2-hydroxybenzenesulfonic acid and 4-aminoantipyrine to a colored product. The FADP-based enzyme amplification cascade has been used in a novel releasable linker immunoassay (RELIA) to quantify thyrotropin (TSH). In the assay, TSH is first captured onto antibody-coated chromium dioxide particles. After formation of an antibody-TSH sandwich with a dethiobiotinylated second antibody, the complex is reacted with a streptavidin-ALP conjugate. Biotin is then used to release the conjugate into solution, and ALP is quantified in an automated version of the FADP-based amplification cascade on the aca discrete clinical analyzer (Du Pont). The sensitivity of the colorimetric RELIA assay for TSH (less than 0.1 milli-int. unit/L) is comparable with that of fluorometric assays. This technology provides a way to adapt to the aca high-sensitivity immunoassays for a wide range of analytes via colorimetric detection.
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PMID:Sensitive, colorimetric enzyme amplification cascade for determination of alkaline phosphatase and application of the method to an immunoassay of thyrotropin. 189 77

Using specific monooxygenase and oxidase inhibitors in a plant cell/microbe coincubation assay, the biochemical mechanisms of the plant activation of two aromatic amines were compared. The biological endpoints included mutation induction, inhibition of mutagenicity, viability of the plant cells (activating system), and viability of the microbial cells (genetic indicator organism). The activation of m-phenylenediamine by TX1 cells was mediated by enzyme systems that were inhibited by diethyldithiocarbamate, potassium cyanide, methimazole, (+)-catechin or acetaminophen. The inhibition by metyrapone was attended by toxicity in the plant cells. These data implicate a TX1 cell peroxidase and a FAD-dependent monooxygenase in the plant activation of m-phenylenediamine. The TX1 cell activation of 2-aminofluorene was inhibited by diethyldithiocarbamate, 7,8-benzoflavone, acetaminophen or (+)-catechin. An additional pathway of the plant cells in the activation of 2-aminofluorene may involve a cytochrome P-448-type N-hydroxylase.
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PMID:The biochemical mechanisms of the plant activation of promutagenic aromatic amines. 216 71

Incubation of the streptococcal NADH peroxidase with 5-thio-2-nitrobenzoate under anaerobic denaturing conditions leads to the rapid incorporation of 1 eq/FAD of the aromatic thiol. Addition of dithiothreitol to the resulting conjugate, following ultrafiltration, demonstrates that a mixed disulfide has been formed. Analysis of the denatured NADH peroxidase by iso-electric focusing reveals the presence of two predominant species differing in isoelectric point by approximately 0.1 units. Preincubation with 20 mM hydrogen peroxide gives essentially complete and irreversible conversion to the more acidic species. Treatment of the native peroxidase with low concentrations of hydrogen peroxide also leads to irreversible enzyme inactivation; the low extinction long wavelength absorbance associated with the enzyme as purified is lost in the process. Anaerobic dithionite and NADH titrations of the peroxide-inactivated enzyme indicate that, while the cysteinyl redox center is nonfunctional, the enzyme is still capable of forming a binary complex with NADH. We propose that the redox-active cysteinyl derivative which serves as the second redox center in the native peroxidase is a stabilized cysteine-sulfenic acid derivative of Cys42. This determination is consistent with the covalent modifications observed with both 5-thio-2-nitrobenzoate and with H2O2 and is supported by mass spectrometric analysis of a chymotryptic cysteinyl peptide derived from the unmodified peroxidase.
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PMID:The non-flavin redox center of the streptococcal NADH peroxidase. II. Evidence for a stabilized cysteine-sulfenic acid. 250 3


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