Search results for "REDUCTASE"
showing 10 items of 798 documents
Determination of Plasma Lipid Hydroperoxides by an NADPH/NADP + Coupled Enzyme Reaction System. Evaluation of a Method
1998
Summary: Several techniques based on different principles have been proposed to measure lipid hydroperoxides. Enzymatic methods are sensitive and can be quite specific but they are subject to interference by inhibitors and not all are stoichiometric. The present work proposes some modifications of the Heath & Tappel (Anal Biochem 1976; 7:184—91) enzymatic method of determination of lipid hydroperoxides in order to standardize and automate it and to meet the analytical criteria required for a biological assay. The proposed new protocol and the automated assay give acceptable within-run and between-run precisions, with coefficients of variation of 3.34% and 5.80%, respectively, at the usual p…
Der cytochemische Nachweis von Prolin-Dehydrogenasen, Acetaldehyd-Dehydrogenasen und Dihydrolipons�ure-Dehydrogenase in den Zellen vonSaccharomyces c…
1967
Using the tetrazolium salt Nitro-BT, the following dehydrogenases can be demonstrated cytochemically in the cells ofSaccharomyces cerevisiae: (1)Proline dehydrogenase activity: it cannot be decided whether the formazan production is a result of L-proline: NAD(P)-2-oxidoreductase (E.C. 1.5.1.1) or of L-proline:NAD(P)-5-oxidoreductase(E.C. 1.5.1.2); (2)Aldehyde dehydrogenase activity: using the coenzymes NAD and NADP and the activators KCl and MgCl2, different reaction pictures are obtained which led to the conclusion that aldehyde: NADP oxidoreductase (E.C. 1.2.1.4) and aldehyde: NAD(P) oxidoreductase (E.C. 1.2.1 5) can be demonstrated seperately; (3)Dihydrolipoic dehydrogenase (E.C. 1.6.4.3…
Reduction of benzo(a)pyrene mutagenicity by dihydrodiol dehydrogenase
1979
THE enigma of how inert chemicals can exert potent mutagenic, carcinogenic, allergenic and cytotoxic effects has been much debated. It has been learned that such compounds are metabolically converted to chemically reactive species1. In the case of aromatic or olefinic compounds, monooxygenases located in the membranes of the cell can transform these compounds into epoxides2–5 which by virtue of electrophilic reactivity can bind chemically to cellular macromolecules such as DNA, RNA and proteins, thereby disturbing biochemical control mechanisms and leading to the above mentioned toxic effects. The same membranes in which such epoxides are produced possess an enzyme, epoxide hydratase, which…
One Enzyme, Two Functions
2010
The human enzyme paraoxonase-2 (PON2) has two functions, an enzymatic lactonase activity and the reduction of intracellular oxidative stress. As a lactonase, it dominantly hydrolyzes bacterial signaling molecule 3OC12 and may contribute to the defense against pathogenic Pseudomonas aeruginosa. By its anti-oxidative effect, PON2 reduces cellular oxidative damage and influences redox signaling, which promotes cell survival. This may be appreciated but also deleterious given that high PON2 levels reduce atherosclerosis but may stabilize tumor cells. Here we addressed the unknown mechanisms and linkage of PON2 enzymatic and anti-oxidative function. We demonstrate that PON2 indirectly but specif…
Selenoproteins, cholesterol-lowering drugs, and the consequences: revisiting of the mevalonate pathway.
2004
3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and peroxisome proliferator-activated receptor alpha activators (fibrates) are the backbone of pharmacologic hypercholesterolemia and dyslipidemia treatment. Many of their clinical effects, however, are still enigmatic. This article describes how a side road of the mevalonate pathway, characterized in recent years, can rationalize a major fraction of these unexplained observations. This side road is the enzymatic isopentenylation of selenocysteine-tRNA([Ser]Sec) (Sec-tRNA), the singular tRNA to decode the unusual amino acid selenocysteine. The functionally indispensable isopentenylation of Sec-tRNA requires a unique interm…
Analogues of cytotoxic squamocin using reliable reactions: new insights into the reactivity and role of the α,β-unsaturated lactone of the annonaceou…
2006
Abstract A small library of squamocin analogues has been prepared and screened biologically (cytotoxicity, inhibition of mitochondrial complex I and complex III). To centre diversity on a crucial part of the molecule (i.e., the α,β-unsaturated lactone), an original and reliable lactone opening reaction has been discovered and exploited among other efficient reactions.
Synthesis and antiproliferative activity of 2'-O-allyl-1-beta-D-arabynofuranosyl-uracil, -cytosine and -adenine
1997
Abstract With the aim to design potential inhibitors of ribonucleotide reductase (RR), 2′-O-allyl-β-D-arabinofuranosyl-uracil ( 4 ), -cytosine ( 7 ) and -adenosine ( 10 ) were prepared and evaluated for their cytostatic activity against Molt4/C8, CEM and L1210 cell lines. Although our preliminary data do not allow to assess if RR is the intracellular target, the results point to differences in the (anti)metabolic behavior of these compounds. This study also offers a general synthesis of 2′-O-allyl-β-D-arabinofuranosyl nucleosides for potential applications in the preparation of 2′-O-allyl-β-D-oligoarabino nucleotides.
Enzymatic biosynthesis of raumacline
1995
Abstract The indole alkaloid, raumacline, is biosynthesized from ajmaline, when the latter was fed to cell suspensions of Rauwolfia serpentina . Formation in catalysed by two enzymes, a cell wall-bound peroxidase followed by a NADPH 2 -dependent reductase. The first enzyme cleaves ajmaline oxidatively leading to a C-21 epimeric mixture of 21-hydroxyraumacline, a novel alkaloid, which, in turn, is reduced under formation of raumacline. The peroxidase reaction is not specific for Rauwolfia cells whereas the reductase is present exclusively in Rauwolfia cell suspensions. The reductase has been purified to homogeneity. The enzyme is highly substrate specific, only accepting 21-hydroxyraumacline…
Nitrate Reductase Activity of Mitochondrial Aldehyde Dehydrogenase (ALDH-2) as a Redox Sensor for Cardiovascular Oxidative Stress
2009
In 2002, mitochondrial aldehyde dehydrogenase (ALDH-2) was identified as an organic nitrate bioactivating enzyme. This so-called nitrate reductase activity denitrates nitroglycerin (glycerol trinitrate) to its 1,2-glycerol dinitrate metabolite and nitrite. This reaction relies on reduced thiols at the active site of the enzyme and on the presence of reduced dithiols as the electron source. During bioconversion of nitroglycerin, and also in the presence of reactive oxygen and nitrogen species, the active site thiols of ALDH-2 are oxidized and the enzyme looses its activity. We, therefore, speculated that ALDH-2 activity could be a useful marker for cardiovascular oxidative stress. Indeed, th…
Die Glucose-Oxydasen aus Penicillium notatum (Notatin) und Aspergillus niger (Nigerin) I. Isolierung und einige molekulare eigenschaften
1965
Summary By chromatography on carboxymethyl- and diethylaminoethyl-Sephadex pure preparations of the glucose oxidases ( β - d -glucose: oxygen oxidoreductase, EC 1.1.3.4) notatin from Penicillium notatum and nigerin from Aspergillus niger could be obtained. Differences in the binding to the cation- and anion-exchangers indicate that these two glucose oxidases differ markedly with respect to the structures of the respective apoenzymes. A mixture of notatin and nigerin can easily be separated by chromatography. Moreover, there are also structural differences in the neighbourhood of the prosthetic flavin-adenine dinucleotide groups. The flavin-adenine dinucleotide spectrum of notatin is shifted…