Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.1.1.1 (alcohol dehydrogenase)
 9,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Microsomes of human polymorphonuclear leukocytes (PMN) in the presence of 100 microM NADPH converted 0.6 microM leukotriene B4 (LTB4) to 20-OH-LTB4 (retention time = 18.0 min) and to two additional compounds designated I (retention time = 16.8 min) and II (retention time = 9.6 min) as analyzed by reverse-phase high performance liquid chromatography (HPLC). Compounds I and II were also formed from the reaction of 1.0 microM 20-OH-LTB4, PMN microsomes, and 100 microM NADPH; the identity of compound II was confirmed as 20-COOH-LTB4 by gas chromatography-mass spectrometry. Equine alcohol dehydrogenase in the presence of 100 microM NAD+ in 0.2 M glycine buffer (pH 10.0) converted 20-OH-LTB4 to 20-aldehyde (CHO) LTB4, which coeluted with compound I on reverse-phase HPLC. In the presence of 100 microM NADH in 50 mM potassium phosphate buffer (pH 6.5), equine alcohol dehydrogenase reduced both 20-CHO-LTB4 and compound I to 20-OH-LTB4, indicating the identity of compound I as 20-CHO-LTB4. Gas chromatography-mass spectrometry of trideuterated O-methyl-oxime trimethylsilyl ether methyl ester derivative of 3H-labeled compound I definitively established compound I as 20-CHO-LTB4. Addition of immune IgG to cytochrome P-450 reductase or 1.0 mM SKF-525A completely inhibited the formation of 20-CHO-LTB4 from 20-OH-LTB4, indicating that the reaction was catalyzed by a cytochrome P-450. LTB5 (3.0 microM), a known substrate for cytochrome P-450LTB and a competitive inhibitor of LTB4 omega-oxidation, completely inhibited the omega-oxidation of 1.5 microM 20-OH-LTB4 to 20-CHO-LTB4, indicating that the cytochrome P-450 was P-450LTB. Conversion of 1.0 microM 20-CHO-LTB4 to 20-COOH-LTB4 by PMN microsomes was also dependent on NADPH and inhibited by antibody to cytochrome P-450 reductase, 1.0 mM SKF-525A, or 5.0 microM LTB5, indicating that this reaction was also catalyzed by cytochrome P-450LTB. These results identify the novel metabolite 20-CHO-LTB4 and indicate that cytochrome P-450LTB catalyzes three sequential omega-oxidations of LTB4 leading to the formation of 20-COOH-LTB4 via 20-OH-LTB4 and 20-CHO-LTB4 intermediates.
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PMID:The identification and formation of 20-aldehyde leukotriene B4. 283 6

Hepatic microsomes of the guinea pig converted delta 8-tetrahydrocannabinol (delta 8-THC) to various oxidized metabolites, including 7 alpha-hydroxy-delta 8-THC (7 alpha-OH-delta 8-THC), 7 beta-OH-delta 8-THC, and 7-oxo-delta 8-THC. The enzyme which mediates biotransformation of 7-OH-delta 8-THCs to 7-oxo-delta 8-THC was characterized in the present study. The oxidative activity was mainly located in microsomes. The microsomal reaction required NADPH and oxygen and showed an optimal pH around 7.5. The reaction was inhibited by beta-diethylaminoethyl diphenylpropylacetate (SKF 525-A), an inhibitor of cytochrome P-450, but not by pyrazole, a specific inhibitor of alcohol dehydrogenase. However, 7-oxo-delta 8-THC formation was not affected by carbon monoxide or by pretreatment of animals with cobaltous chloride (40 mg/kg, ip, once a day for 3 days). Atmospheric oxygen was incorporated into 7-oxo-delta 8-THC formed from 7 alpha-OH-delta 8-THC, but not into that from 7 beta-OH-delta 8-THC. Further, 7-oxo-delta 8-THC formed from 7 alpha-18OH-delta 8-THC released about half of 18O at the 7-position, whereas the 7-oxo metabolite from 7 beta-18OH-delta 8-THC lost little of the isotope at the 7 beta-position during the oxidative reaction. From these results, it is likely that hepatic microsomal monooxygenase (probably cytochrome P-450) plays a main role in the oxidation. In addition, mechanisms for 7-oxo-delta 8-THC formation from 7 alpha-OH-delta 8-THC or 7 beta-OH-delta 8-THC are different.
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PMID:Enzymatic oxidation of 7-hydroxylated delta 8-tetrahydrocannabinol to 7-oxo-delta 8-tetrahydrocannabinol by hepatic microsomes of the guinea pig. 289 47

Elimination of [2H]ethanol in vivo as studied by gas chromatography/mass spectrometry occurred at about half the rate in deer mice reported to lack alcohol dehydrogenase (ADH-) compared with ADH+ deer mice and exhibited kinetic isotope effects on Vmax and Km (D(V/K] of 2.2 +/- 0.1 and 3.2 +/- 0.8 in the two strains, respectively. To an equal extent in both strains, ethanol elimination was accompanied by an ethanol-acetaldehyde exchange with an intermolecular transfer of hydrogen atoms, indicating the occurrence of dehydrogenase activity. This exchange was also observed in perfused deer mouse livers. Based on calculations it was estimated that at least 50% of ethanol elimination in ADH- deer mice was caused by the action of dehydrogenase systems. NADPH-supported cytochrome P-450-dependent ethanol oxidation in liver microsomes from ADH+ and ADH- deer mice was not stereoselective and occurred with a D(V/K) of 3.6. The D(V/K) value of catalase-dependent oxidation was 1.8, whereas a kinetic isotope effect of cytosolic ADH in the ADH+ strain was 3.2. Mitochondria from both ADH+ and ADH- deer mice catalyzed NAD+-dependent ethanol oxidation and NADH-dependent acetaldehyde reduction. The kinetic isotope effects of NAD+-dependent ethanol oxidation in the mitochondrial fraction from ADH+ and ADH- deer mice were 2.0 +/- 0.1 and 2.3 +/- 0.3, respectively. The results indicate only a minor contribution by cytochrome P-450 to ethanol elimination, whereas the isotope effects are consistent with ethanol oxidation by the catalase-H2O2 system in ADH- deer mice in addition to the dehydrogenase systems.
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PMID:Dehydrogenase-dependent ethanol metabolism in deer mice (Peromyscus maniculatus) lacking cytosolic alcohol dehydrogenase. Reversibility and isotope effects in vivo and in subcellular fractions. 292 22

Deermice lacking the low-Km alcohol dehydrogenase eliminated butan-1-ol, a substrate for microsomal oxidation but not for catalase, at 117 mumol/min per kg body wt. Microsomal fractions and hepatocytes metabolized butan-1-ol also (Vmax. = 6.7 nmol/min per nmol of cytochrome P-450, Km = 0.85 mM; Vmax. = 5.3 nmol/min per 10(6) cells, Km = 0.71 mM respectively). These results are consistent with alcohol oxidation by the microsomal system in these deermice.
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PMID:Characteristics of butanol metabolism in alcohol dehydrogenase-deficient deermice. 293 Apr 72

Reports from several laboratories agree that many, but not all, aliphatic nitriles undergo hepatic biotransformation in mice and rats to release free cyanide, but the mechanisms at work in these reactions remain in doubt. We have used primarily n-butyronitrile, propionitrile, and their respective alpha-carbon-hydroxylated homologs, propionaldehyde cyanohydrin and lactonitrile, to examine this question in mice. Pretreatment of mice with the hepatic microsomal enzyme inducers, pregnenolone-16 alpha-carbonitrile, troleandomycin, and isosafrole, or with the cytochrome P-450-depleting agent, cobaltous chloride, did not influence the mortality of mice given single doses of nitriles. Repeated injections of aspirin or sodium salicylate in water failed to protect mice against death by the nitriles. Dimethyl sulfoxide, however, was effective in reducing mortality after nitrile administration. Repeated injections of 4-methylpyrazole or disulfiram protected mice against death after nitriles. Most of the treatment regimens successful against the nitriles also protected against death due to the cyanohydrins. The cyanohydrins were more acutely toxic than their parent nitriles, produced death much more rapidly, and resulted in the same toxic signs, suggesting that they are intermediates in the bioactivation pathway leading to free cyanide. The cyanohydrins appeared to serve as weak substrates for yeast alcohol dehydrogenase, however, incubation of them with either yeast or horse liver alcohol dehydrogenase did not increase the rate of cyanide release over that in incubations where the enzymes were absent. The slow rate of cyanide release due to spontaneous hydrolysis interfered with the determinations of alcohol dehydrogenase activity, but it cannot account for the rapid action and high toxicity of the cyanohydrins in vivo, or for the efficacy of the treatment regimens which protected against death. It appears unlikely that prostaglandin synthetase or alcohol dehydrogenase are importantly involved in nitrile bioactivation. The same active process, however, appears to be responsible both for alpha-carbon hydroxylation and for the subsequent degradation of the resulting cyanohydrins to release free cyanide. It is far more efficient in mediating the latter reaction than the former.
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PMID:Pathways for the bioactivation of aliphatic nitriles to free cyanide in mice. 294 99

Intact periportal (pp) or perivenous (pv) hepatocytes were prepared by digitonin-collagenase liver perfusion. The degree of separation was indicated by significant differences between the pp and pv cells in their activity of the pp markers, alanine aminotransferase (pp/pv = 2.1), gamma-glutamyltranspeptidase (3.4) and lactate dehydrogenase (1.3), and of the pv markers, glutamate dehydrogenase (0.73) and pyruvate kinase (0.81). This pattern was not altered by a 3-day pretreatment with phenobarbital (PB). The hepatocytes isolated from the pv area contained higher activities of microsomal NADPH-cytochrome c reductase, 7-ethoxycoumarin O-deethylase, 7-ethoxyresorufin O-deethylase and benzo(a)pyrene hydroxylase, and of cytosolic glutathione transferase. Cytochrome P-450 and UDP-glucuronosyltransferase were slightly higher in pv cells. Treatment with PB induced NADPH-cytochrome c reductase, glutathione transferase, cytochrome P-450 and UDP-glucuronosyltransferase but the degree of induction was found to be at least as strong in pp cells as in pv cells. The induction of 7-ethoxyresorufin O-deethylase and 7-ethoxycoumarin O-deethylase was clearly more prominent in pp cells. On the other hand, PB reduced the activities of benzo(a)pyrene hydroxylase and alcohol dehydrogenase in both cell types. These results demonstrate by direct enzyme assay of separated cells the dominance of the pv-region for metabolizing drugs in the normal liver. Contrary to several other studies, however, our data indicate that induction by PB occurs panacinarily, i.e., relatively more in the pp region, thus diminishing rather than exaggerating the original pv dominance.
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PMID:Effect of phenobarbital on the distribution of drug metabolizing enzymes between periportal and perivenous rat hepatocytes prepared by digitonin-collagenase liver perfusion. 302 20

Lipoperoxidation, a degradative process of membranous polyunsaturated fatty acids, has been suggested to represent an important mechanism in the pathogenesis of ethanol toxicity on the liver and possibly also on the brain. Catalysis by transition metals, especially iron, is involved in the biosynthesis of free radicals contributing to lipid peroxidation. Although the exact nature of the redox-active iron implicated in this catalysis is still unknown, it has been well established that lipid peroxidation can be prevented in vitro by iron chelators such as desferrioxamine. Deprivation of redox-active iron through desferrioxamine inhibits by about 50% the microsomal oxidation of ethanol in vitro and reduces very significantly in vivo the overall ethanol elimination rate in rats. Administration of desferrioxamine together with ethanol also reduces the ethanol-induced disturbances in the antioxidant defense mechanisms of the hepatocyte. It also reduces in mice both the severity of physical dependence on ethanol and lethality following the acute administration of a narcotic dose of ethanol. Chronic overloading of rats with iron results, on the opposite, in an increased rate of ethanol elimination, although alcohol dehydrogenase and catalase activities are reduced and cytochrome P-450 depleted in the liver of such iron-overloaded animals. The magnitude of the ethanol-induced increase in lipid peroxidation and decrease in the major membranous antioxidant, alpha-tocopherol, is exacerbated in iron-overloaded rats. Several disturbances of iron metabolism have been reported in human alcoholics. Their contribution to ethanol toxicity appears very likely in the case of hepatic siderosis associated with alcohol abuse. Ethanol could however disturb iron metabolism even in the absence of gross abnormalities of the total iron stores. It is suggested that ethanol intoxication could increase cellular redox-active iron, thus contributing to an enhanced steady-state concentration of reactive-free radicals. This oxidative stress would lead to lipoperoxidative damage and cellular injury.
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PMID:Involvement of iron and iron-catalyzed free radical production in ethanol metabolism and toxicity. 303 5

Pyrazole, an effective inhibitor of alcohol dehydrogenase, was previously shown to be a scavenger of the hydroxyl radical. 4-Hydroxypyrazole is a major metabolite in the urine of animals administered pyrazole in vivo. Experiments were conducted to show that 4-hydroxypyrazole was a product of the interaction of pyrazole with hydroxyl radical generated from three different systems. The systems utilized were the iron-catalyzed oxidation of ascorbate, the coupled oxidation of hypoxanthine by xanthine oxidase, and NADPH-dependent microsomal electron transfer. Ferric-EDTA was added to all the systems to catalyze the production of hydroxyl radicals. A HPLC procedure employing either uv detection or electrochemical detection was utilized to assay for the production of 4-hydroxypyrazole. The three systems all supported the oxidation of pyrazole to 4-hydroxypyrazole by a reaction which was sensitive to inhibition by competitive hydroxyl radical scavengers such as ethanol, mannitol, or dimethyl sulfoxide and to catalase. The sensitivity to catalase implicates H2O2 as the precursor of the hydroxyl radical by all three systems. Superoxide dismutase inhibited production of 4-hydroxypyrazole only in the xanthine oxidase reaction system. In the absence of ferric-EDTA (and azide), microsomes catalyzed the oxidation of pyrazole to 4-hydroxypyrazole by a cytochrome P-450-dependent reaction which was independent of hydroxyl radicals. This latter pathway may be primarily responsible for the in vivo metabolism of pyrazole to 4-hydroxypyrazole. The production of 4-hydroxypyrazole from the interaction of pyrazole with hydroxyl radicals may be a sensitive, rapid technique for the detection of these radicals in certain tissues or under certain conditions, e.g., increasing oxidative stress.
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PMID:Production of 4-hydroxypyrazole from the interaction of the alcohol dehydrogenase inhibitor pyrazole with hydroxyl radical. 303 2

Rat cytochrome P-450(M-1) cDNA was expressed in Saccharomyces cerevisiae TD1 cells by using a yeast-Escherichia coli shuttle vector consisting of P-450(M-1) cDNA, yeast alcohol dehydrogenase promoter and yeast cytochrome c terminator. The yeast cells synthesized up to 2 X 10(5) molecules of P-450(M-1) per cell. The microsomal fraction prepared from the transformed cells contained 0.1 nmol of cytochrome P-450 per mg of protein. The expressed cytochrome P-450 catalyzed 16 alpha- and 2 alpha-hydroxylations of testosterone in accordance with the catalytic activity of P-450(M-1), but did not hydroxylate vitamin D3 or 1 alpha-hydroxycholecalciferol at the 25 position. The expressed cytochrome P-450 also catalyzed the oxidation of several drugs and did not show 25-hydroxylation activity toward 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol. However, it cross-reacted with the polyclonal and monoclonal antibodies elicited against purified P-450cc25 which catalyzed the 25-hydroxylation of vitamin D3. These results indicated that P-450(M-1) cDNA coded the 2 alpha- and 16 alpha-hydroxylase of testosterone, and that these two positions of testosterone are hydroxylated by a single form of cytochrome P-450. Vitamin D3 25-hydroxylase and testosterone 16 alpha- and 2 alpha-hydroxylase are different gene products, although these two hydroxylase activities are immunochemically indistinguishable.
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PMID:Expression of a rat liver microsomal cytochrome P-450 catalyzing testosterone 16 alpha-hydroxylation in Saccharomyces cerevisiae: vitamin D3 25-hydroxylase and testosterone 16 alpha-hydroxylase are distinct forms of cytochrome P-450. 305 77

Advances in our knowledge of the microsomal metabolism of ethanol enable us to understand a number of complications that develop in the alcoholic. After chronic ethanol consumption, microsomal ethanol-oxidizing system (MEOS) activity increases with an associated rise in microsomal cytochrome P-450, including a form different from that induced by phenobarbital and methylcholanthrene and which has a high affinity for ethanol, as shown in reconstituted systems. The role of this MEOS in vivo and its increase after chronic ethanol consumption was most conclusively shown in alcohol dehydrogenase-negative deer mice. Microsomal induction is also associated with enhanced metabolism of other drugs, resulting in metabolic drug tolerance. Furthermore, there is increased conversion to toxic metabolites of known hepatotoxic agents (such as CCl4), which may explain the enhanced susceptibility of alcoholics to the toxicity of industrial solvents. Furthermore, the ethanol-induced form of cytochrome P-450 has a high capacity for the conversion to toxic metabolites of some commonly used drugs, such as acetaminophen, and also carcinogens, such as dimethylnitrosamine which is activated at concentrations much lower than those required for other microsomal inducers. Moreover, catabolism of retinol is accelerated through a newly discovered microsomal pathway, thereby contributing to hepatic vitamin A depletion and possibly vitamin A toxicity. There is also induction of microsomal enzymes involved in lipoprotein production, resulting in hyperlipemia. Contrasting with the chronic effects of ethanol consumption, acutely, ethanol inhibits the metabolism of other drugs through competition for an at least partially shared microsomal detoxification pathway.
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PMID:Microsomal ethanol-oxidizing system. 310 31


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