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

NAD(P)H dehydrogenase (EC 1.6.99.2) purified from rat liver cytosol revealed three discrete bands, of mol.wts. about 27000, 18000 and 9000, when subjected to polyacrylamidegel electrophoresis in the presence of sodium dodecyl sulphate. Elution of the bands from the gel and individual re-electrophoresis on separate gels showed that the 27000-mol.wt. band yielded three bands similar to those obtained with the intact enzyme, whereas the 18000-mol.wt. band retained its characteristic mobility. Amino acid analysis of native enzyme and protein extracted from each of the three bands from sodium dodecyl sulphate/polyacrylamide gels suggests that the native enzyme is composed of two subunits and that each subunit consists of two dissimilar non-covalently bound polypeptides, so that altogether the enzyme is composed of four polypeptides, two of mol.wt. 18000 and two of mol.wt. 9000. NAD(P)H dehydrogenase was active over a wide pH range with no sharp optimum. The same K(m) value for NADH but different values for V(max.) were obtained for the enzyme purified from Sprague-Dawley and Wistar rats. In immunodiffusion, however, the enzymes from the two rat strains showed a reaction of complete identity. NAD(P)H dehydrogenase was effectively inhibited by thiol-blocking reagents, indicating that the activity is dependent on free thiol group(s). By amino acid analysis six cysteine residues were found per mol of enzyme. Guanidino-group- and amino-group-selective reagents had only moderate inactivating effects on the enzyme activity.
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PMID:Some molecular properties of NAD(P)H dehydrogenase from rat liver. 48 48

The organic phosphate allosteric effectors of hemoglobin, inositol hexaphosphate, 2,3-diphosphoglycerate, and ATP, interact with NADH-methemoglobin reductase (NADH-diaphorase). Significant inhibitory effects on the enzyme were found when dichlorophenolindophenol, or ferricyanide were used as electron acceptors in place of methemoglobin. In contrast, apparent stimulation of enzyme activity was observed when adult human methemoglobin was used as the electroganic phosphate on the rate of reaction due to its interaction with the substrate methemoglobin to produce the favored T type of quaternary conformation. The inhibitory effect of inositol hexaphosphate on the enzyme is associated with a perturbation in the reactivity of essential sulfhydryl group(s) on the enzyme. It is suggested that the interaction of the organic phosphate with the enzyme as well as with the substrate is significant in determining the overall rate of methemoglobin reduction.
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PMID:Inhibition of NADH-methemoglobin reductase by organic phosphates. 49 34

The kinetic properties of cytosolic and solubilized mitochondrial menadione reductases (EC 1.6.99.2) from rat liver were compared. The mechanism of the reaction of cytosolic and mitochondrial menadione reductases with NADH and 4-anilino-5-methoxy-1,2-benzoquinone (AMOBQ) as substrates obeys the "ping-pong" kinetics. AMOBQ is a competitive inhibitor of cytosolic menadione reductase (Ki = 219 microM). Both menadione reductases have similar or identical values of true and effective kinetic constants and similar electrophoretic mobilities.
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PMID:[Comparative analysis of cytosolic and solubilized mitochondrial menadione reductases from rat liver]. 49 67

The effect of 4'-demethyl-epipodophyllotoxin-beta-D-thenylidene glucoside (VM-26) , a semi-synthetic derivative of podophyllotoxin, on the cell cycle was studied with chick embryo fibroblasts cultivated in vitro. DNA, RNA and protein content, as well as NADH-diaphorase activity were determined by quantitative microdensitometry and cytofluorometry. The incorporation of [3H]thymidine and [3H]leucine into DNA and proteins were analysed by autoradiography. These metabolic data correlated with morphological observation showed that VM-26 blocks the cell cycle at different moments of its kinetics depending on both the dose and the time exposure. NADH-diaphorase activity is the first to be affected, then biochemical changes (involving the metabolism of RNA and proteins) and morphological alterations (especially of mitochondria) follow. This suggests that VM-26 may act primarily upon the mechanism of respiration of the cell.
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PMID:A quantitative microdensitometric and autoradiographic study of the effect of 4'-demethyl-epipodophyllotoxin-beta-D-thenylidene glucoside (VM-26) on the cell cycle of cultured fibroblasts. 53 43

Histochemical and biochemical studies on the folate metabolism (folic acid an its principal enzyme-dihydrofolate-reductase) in bovine cortex - gyrus marginallis in the process of ageing were performed, in parallel with NADH2-cytocrom-C-reductase (diaphorase). Folic acid and folate enzyme, weak positive in neurons in young age, increased in old age in nerve cells and especially in their processes and in capillaries. The diaphorase strongly increased in all cells, glia and vessels, in old age.
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PMID:Histochemical study on the dihydrofolatereductase and folic acid in mammalian brain cortex. 54 85

1. Pig heart lipoamide dehydrogenase (NADH: lipoamide oxidoreductase, EC 1.6.4.3) has been immobilised to Sepharose by thiol-disulphide interchange via a series of thiolated spacer molecules of increasing length. A number of properties of the immobilised enzyme have been investigated in order to ascertain the effects of proximity to the matrix backbone. 2. Proximity to the matrix backbone reduced the specific activity for lipoamide as substrate but enhanced by 3-8-fold the diaphorase activity with 2,6-dichloroindophenol. These observations are explained in part by an increase in the apparent Km for lipoamide when the enzyme is covalently attached to Sepharose via a short spacer molecule. 3. Both the thermal stability at 90 degrees C and the stability in 30% (v/v) dioxane are enhanced by up to 200% when the enzyme resides close to the matrix but approach those of the native enzyme as the length of the spacer molecule is increased. 4. These data have been correlated with measures of the accessibility of the enzyme as the nominal length of the spacer arm was increased. Thus, as the chain length increased, the rate of cleavage of the disulphide linkage between the enzyme and spacer increased and the enzyme became more susceptible to proteolysis by thermolysin. In contrast, increasing the chain length of the spacer made the enzyme less amenable to inhibition by a specific antibody. 5. These data are discussed in terms of the effect of the matrix on the conformation of the bound enzyme.
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PMID:Immobilised lipoamide dehydrogenase. 2. Properties of the enzyme immobilised to agarose through spacer molecules of various lengths. 56 Sep 66

NADH and NADPH diaphorase isozymes have been studied in human tissues. Evidence from rare heterozygotes suggests that the red cell and main tissue forms of NADH diaphorase are products of the same locus DIA1. NADPH-dependent diaphorase appears to be the product of a second locus DIA2. A third locus, DIA3, codes for the polymorphic sperm diaphorase. The products of this locus are also found in foetal tissues including placenta and adult brain and gonads. The products of these three loci may be distinguished by their substrate specificity, thermostability and molecular size.
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PMID:An interpretation of human diaphorase isozymes in terms of three gene loci DIA1, DIA2 and DIA3. 56 99

Spinach nitrate reductase complex previously inactivated by treatment with mercurials p-hydroxymercuribenzoate or p-hydroxymercuriphenyl sulphonate can be reactivated by incubation with dithioerythritol. The reactivation of NADH-diaphorase seems to be FAD-dependent, whereas that of FNH2-nitrate reductase is not. The requirement of FAD for NADH-inactivation of nitrate reductase treated with p-hydroxymercuribenzoate disappears after treatment with dithioerythritol.
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PMID:Nitrate reductase from Spinacea oleracea. FAD and the reactivation of the enzyme treated with p-Hydroxymercuribenzoate. 59 86

We describe a highly sensitive and accurate automated continuous-flow method for determining bile acids in serum. The bile acids are first liberated from serum protein by dialysis at alkaline pH and then measured fluorometrically after the following enzymic reaction. Bile acids are converted to 3-oxo bile acids with 3alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) with concomitant reduction of NAD+ to NADH. The hydrogen in the generated NADH is transferred by diaphorase (EC 1.6.4.3) to resazurin to yield resorfin, the fluorophore. Only 100 microliter of serum is required and 40 determinations can be done per hour. The CV for 20 replicate determinations in serum with a mean bile acid concentration of 9.8 mumol/liter was 2.6%. The CV for day-to-day variation for another serum on 27 successive days was 3.0% (mean concentration, 10.0 mumol/liter). We applied this method to 826 sera from various diseases; 29% exceeded the upper limit of normal, 10 mumol/liter, and abnormally high values (greater than 20 mumol/liter) were almost exclusively limited to sera from hepatobiliary and enteric disorders.
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PMID:Continuous-flow determination of bile acids in serum, and its clinical application. 65 94

Comparative analyses of the fibre content (FG, FOG, and SO fibres) and the capillary density (the number of capillaries surrounding individual fibres and the capillary/fibre ratio) were performed in hind limb muscles of the cat. Cross-sections from the tenuissimus, the biceps femoris, the lateral head (LG) and the medial head (MG) of the gastrocnemius and the soleus were cut in a cryostat. The sections were stained histochemically for the NADH2-diaphorase and alkaline (pH 9.4) actomyosin ATPase activity, which enables differentiation of different types of fibres. The endothelium of the capillaries was identified via staining for unspecific alkaline ATPase activity. The number of capillaries surrounding each individual muscle fibre had a positive correlation, first to the oxidative capacity and secondly to the average diameter of the fibres. The thin tenuissimus muscle did not differ in this respect from the thicker muscles. The highest proportion of SO fibres was found in the soleus and the MG muscles. FG fibres of two different types were dominating the fibre mass in the biceps femoris and the LG muscles, while the tenuissimus contained more FOG fibres than these muscles. In general the FG fibres had a larger diameter than the FOG and the SO fibres. The soleus and the MG muscles contained larger fibres than the other examined muscles. FG fibres were surrounded by fewer capillaries than FOG and SO fibres. The soleus and the MG muscles, with a higher percentage of SO fibres and also larger fibres, had the largest number of capillaries around the fibres and the highest capillary/fibre ratio.
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PMID:Capillary supply of the muscle fibre population in hindlimb muscles of the cat. 66 57


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