Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.5.2 (NQO1)
 6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Short-term treatment of rats with hepatocarcinogens elicits a consistent pattern of phenotypic changes in hepatic drug metabolizing enzymes, the most striking of which is a marked increase in microsomal epoxide hydrolase (EH) activity. The antihistaminic drug methapyrilene induces a high incidence of hepatocellular carcinoma in F-344 rats. The studies reported here were designed to assess the effects of methapyrilene on hepatic EH activity, cytochrome P-450-dependent mixed-function oxidase activities, liver morphology, and liver-derived serum enzymes. Male F-344 rats were treated with three daily oral doses of methapyrilene-HCl, up to 300 mg/kg/day, and were sacrificed 48 hr after the last dose. Hepatic microsomal EH and cytosolic DT-diaphorase activities were increased in a dose-related fashion, to 420 and 230% of control, respectively. Cytochrome P-450 content and benzphetamine-N-demethylase and ethoxycoumarin-O-deethylase activities were concomitantly decreased to 35-50% of control. Serum gamma-glutamyl transpeptidase and alanine aminotransferase activities were elevated 22- to 27-fold, and serum bile acids to 36-fold by treatment with methapyrilene. Periportal lesions, characterized by inflammation, nuclear and nucleolar enlargement, bile duct hyperplasia, and hepatocellular necrosis, were observed following methapyrilene administration. The severity of the periportal lesion correlated with elevations in the serum chemistry parameters. The increases noted in microsomal EH activity supports the suggestion that this enzyme may be a useful biochemical marker for exposure to hepatocarcinogens.
 ...
PMID:Effects of methapyrilene on rat hepatic xenobiotic metabolizing enzymes and liver morphology. 285 28

Vitamin K-dependent carboxylase activity has been demonstrated in the crude microsomal fraction of the intima of bovine aortae. The procedure for the isolation of vessel wall carboxylase is a slight modification of the general preparation procedure for tissue microsomes. The highest activity of the non-hepatic enzyme was observed at 25 degrees C and hardly any NADH-dependent vitamin K reductase could be demonstrated. The optimal reaction conditions for both vessel wall as well as liver carboxylase were similar: 0.1 M-NaCl/0.05 M-Tris/HCl, pH 7.4, containing 8 mM-dithiothreitol, 0.4% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonic acid (CHAPS), 0.4 mM-vitamin K hydroquinone and 2 M-(NH4)2SO4. Warfarin inhibits the hepatic and non-hepatic carboxylase/reductase enzyme complex more or less to a similar degree. We have measured the apparent Km values for the following substrates: Phe-Leu-Glu-Glu-Leu ('FLEEL'), decarboxylated osteocalcin, decarboxylated fragment 13-29 from descarboxyprothrombin and decarboxylated sperm 4-carboxyglutamic acid-containing (Gla-)protein. The results obtained demonstrated that liver and vessel wall carboxylase may be regarded as isoenzymes with different substrate specificities. The newly discovered enzyme is the first vitamin K-dependent carboxylase which shows an absolute substrate specificity: FLEEL and decarboxylated osteocalcin were good substrates for vessel wall carboxylase, but decarboxylated fragment 13-29 and decarboxylated sperm Gla-protein were not carboxylated at all.
 ...
PMID:Isolation and partial characterization of a vitamin K-dependent carboxylase from bovine aortae. 349 40

A rapid enzymatic method was developed for the assay of serum argininosuccinate lyase (ASAL: EC 4.3.2.1) which is a useful marker enzyme for diagnosis of parenchymal liver diseases. Fumarate, liberated from argininosuccinate in the lyase-mediated reaction, was converted to pyruvate via L-malate by the actions of fumarase and malic enzyme in the presence of NADP+. The NADPH formed was then oxidized with a diaphorase-resazurin system to give a highly fluorescent resorufin. All the enzymatic reactions proceeded continuously in 0.1 M Tris-HCl buffer (pH 7.5) and allowed direct assay of ASAL in serum by monitoring the increase in the fluorescence intensity due to resorufin. The method is rapid and sensitive; only 50 microliter of serum is required. This method was used to detect increases in the activities in sera from patients with liver diseases.
 ...
PMID:An enzymatic method for the assay of serum argininosuccinate lyase. 367 95

Intrinsic NADPH diaphorase activity is a component of the membrane-bound NAD(P)H:O2 oxidoreductase of human neutrophils. NADH-specific diaphorase activity is also present in membrane fractions rich in oxidoreductase activity. Studies were undertaken to determine whether the NADH diaphorase might also be intrinsic to the oxidoreductase. The latter diaphorase was freed from the membrane by detergent extraction and partially purified approximately 80-fold. Its apparent molecular weight following solubilization in deoxycholate and Tween-20 was 204 000 +/- 10 000. The specific activity of the partially purified diaphorase with ferricyanide as electron acceptor was 7.6 X 10(3) mU/mg protein, its pH optimum was 7.0, and its Km for NADH was 13 microM. It is completely devoid of NADPH diaphorase activity, lacks the capacity to reduce molecular oxygen, yet readily reduces ferricyanide, 2,6-dichlorophenolindophenol and ferricytochrome c. Whereas the NADH diaphorase was freed from the particulate fraction of cell lysates by extraction in 10 mM Tris-HCl buffer (pH 8.6) made up in 15% glycerol and 0.5% Tween-20, NADPH-dependent diaphorase and superoxide-generating activities also present in the membrane were not. These observations make it unlikely that the principal membrane-bound NADH diaphorase found in human neutrophils is a component of the NAD(P)H:O2 oxidoreductase, despite its common association in the same particulate fraction of cell lysates.
 ...
PMID:Purification and resolution of NADH diaphorase activity from NADPH diaphorase-linked: O2 oxidoreductase activity of human neutrophils. 384 37

An enzymatic method for determining L-malic acid in wine based on an L-malate sensing layer with nicotinamide adenine dinucleotide (NAD+), L-malate dehydrogenase (L-MDH) and diaphorase (DI), immobilized by sol-gel technology, was constructed and evaluated. The sol-gel glass was prepared with tetramethoxysilane (TMOS), water and HCl. L-MDH catalyzes the reaction between L-malate and NAD+, producing NADH, whose fluorescence (lambdaexc=340 nm, lambdaem=430 nm) could be directly related to the amount of L-malate. NADH is converted to NAD+ by applying hexacyanoferrate(III) as oxidant in the presence of DI. Some parameters affecting sol-gel encapsulation and the pH of the enzymatic reaction were studied. The sensing layer has a dynamic range of 0.1-1.0 g/L of L-malate and a long-term storage stability of 25 days. It exhibits acceptable reproducibility [sr(%) approximately 10] and allows six regenerations. The content of L-malic acid was determined for different types of wine, and polyvinylpolypyrrolidone (PVPP) was used as a bleaching agent with red wine. The results obtained for the wine samples using the sensing layer are comparable to those obtained from a reference method based on UV-vis molecular absorption spectrometry, if the matrix effect is corrected for.
 ...
PMID:Fluorescent sensing layer for the determination of L-malic acid in wine. 1720 64

With a view to their use in the kinetic resolution of racemic non-natural amino acids, five variants of the enzyme L-phenylalanine dehydrogenase, the wild-type enzyme from Bacillus sphaericus and four active-site mutants, have been tested with a range of amino acids. In each case, the rates of reaction with 0.2 mM L-amino acid and with the racemic mixture at 0.4 mM were compared, so that the starting concentration of the active substrate was kept constant. Although the D-amino acids are not substrates, they were inhibitory in all cases. The extent of inhibition, however, varied greatly from compound to compound and among the mutants. With the N145L mutant and DL 4-O-Me-Phe, the equimolar D-enantiomer gave 83.2% inhibition, and with the wild-type enzyme there was 86.7% inhibition with racemic norleucine. By contrast, with these same substrates the N145V mutant showed less than 9% and 24% inhibition respectively. The N145A mutant was selected for use with DL-4-Cl-Phe. The pH was decreased from the enzyme's optimum of 10.4 to 9.5 to minimise breakdown of the coenzyme NAD(+), and the coenzyme was recycled by molecular oxygen with the assistance of a commercial diaphorase. Reaction on a 200 micromole scale in 20 ml ethanolamine HCl buffer, pH 9.5, with 25 microg N145A enzyme and 100 microg diaphorase, was monitored by chiral HPLC. The L-isomer was removed to an extent of >99% after 40 h, with the D-isomer peak undiminished. The pure D-isomer was isolated from the reaction mixture in 85% overall yield after ion-exchange chromatography.
 ...
PMID:Engineered dehydrogenase biocatalysts for non-natural amino acids: efficient isolation of the D-enantiomer from racemic mixtures. 1908 64

Four compounds, including one new lignan cavaol H (1), one new coumarinolignoid 5'-hydroxycleomiscosin B (4) and two known lignans (2-3) were isolated from the 95% ethanol extract of the twigs of Eurycorymbus cavaleriei. Their structures were established on the basis of various spectroscopic analyses including 1D-(1H, 13C, and DEPT) and 2D-NMR (COSY, HMQC, and HMBC). The absolute stereochemistry of the two known lignans was firstly reported in this article by 1H NMR studies on Mosher's ester derivatives. In the present study, quinone reductase induction activities of compounds 1-4 were assayed, compound 4 showed moderate quinone reductase induction with concentration to double the enzyme activity (CD) of 10.5 +/- 0.8 microg/mL. Then we established LC-MS-MS analysis of glutathione (GSH) incubation with compound 4 to explain whether compound 4 induced quinone reductase through alkylating of the sulfhydryl groups of Keap1. Reconstructed selected ion chromatogram (SIC) of m/z 706 after compound 4 incubation with GSH was different from that with Tris-HCl buffer solution, which meant the quinone reductase induction activity of compound 4 attributed to alkylating the sulfhydryl groups of Keap1.
 ...
PMID:Three lignans and one coumarinolignoid with quinone reductase activity from Eurycorymbus cavaleriei. 1937 6