Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.3 (diaphorase)
 5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adrenodoxin, purified from bovine adrenal cortex, was subjected to trypsin cleavage to yield a trypsin-resistant form, designated TT-adrenodoxin. Sequencing with carboxypeptidase Y identified the trypsin cleavage site as Arg-115, while Edman degradation indicated no NH2-terminal cleavage. Native adrenodoxin and TT-adrenodoxin exhibited similar affinity for adrenodoxin reductase as determined in cytochrome c reductase assays. In side chain cleavage assays using cytochrome P-450scc, however, TT-adrenodoxin demonstrated greater activity than adrenodoxin with cholesterol, (22R)-22-hydroxycholesterol, or (20R,22R)-20,22-dihydroxycholesterol as substrate. This enhanced activity is due to increased affinity of TT-adrenodoxin for cytochrome P-450scc; TT-adrenodoxin exhibits a 3.8-fold lower apparent Km for the conversion of cholesterol to pregnenolone. TT-Adrenodoxin was also more effective in coupling with cytochrome P-450(11) beta, exhibiting a 3.5-fold lower apparent Km for the 11 beta-hydroxylation of deoxycorticosterone. In the presence of partially saturating cholesterol, TT-adrenodoxin elicited a type I spectral shift with cytochrome P-450scc similar to that induced by adrenodoxin, and spectral titrations showed that oxidized TT-adrenodoxin exhibited a 1.5-fold higher affinity for cytochrome P-450scc. These results establish that COOH-terminal residues 116-128 are not essential for the electron transfer activity of bovine adrenodoxin, and the differential effects of truncation at Arg-115 on interactions with adrenodoxin reductase and cytochromes P-450 suggest that the residues involved in the interactions are not identical.
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PMID:Adrenodoxin with a COOH-terminal deletion (des 116-128) exhibits enhanced activity. 291 75

1. Effects of two doses of cyproterone acetate (CA) and flutamide (FLU) (50 and 100 mg/kg/3 days) on the testicular steroidogenesis in male rats have been investigated, by measuring the content of cytochrome P-450, cytochrome b5 and cytochrome c reductase activity in the microsomal fraction. 2. CA provoked a significant decrease in cytochrome P-450 content while FLU induced an increase with the lowest dose but a significant decrease after administration of 100 mg/kg. 3. On the other hand, in all cases the cytochrome b5 and cytochrome c reductase activity remained unchanged. 4. The plasma levels of LH and testosterone were measured after CA and FLU injection (50 and 100 mg/kg/3 days). 5. CA administration provoked a reduction in blood levels of these hormones while FLU induced a significant increase in both. 6. These data suggested that CA and FLU modified the cytochrome P-450 in rat testes by an indirect mechanism, probably through the modification of LH plasma levels.
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PMID:Microsomal effects of cyproterone acetate and flutamide in rat testis. 297 Sep 87

Microsomal preparations isolated from rat liver were used to study the action of 2.2'-pyridylisatogen tosylate (PIT) on aniline hydroxylation, cytochrome c reduction and NADPH oxidation. PIT was found to inhibit both the NADPH-dependent (5-100 microM, PIT) and the NADPH-independent (0.05-2.5 mM, PIT) hydroxylation of aniline, but had no significant effect on either the NADPH-dependent oxidation of hexobarbital, or the NADPH-independent hydrolysis of glucose-6-phosphatase. PIT was also found to inhibit cytochrome c reductase competitively (Ki = 35 microM) and to stimulate NADPH oxidation (ED50 = 6.5 microM) PIT and aniline were both found to bind to the microsomal haemoprotein cytochrome P-450 and produce Type II spectral changes. It is proposed that PITs ability to bind to the haemoprotein and its ability to accept electrons from the microsomal NADPH-cytochrome c reductase system leads to the inhibition of aniline hydroxylase activity.
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PMID:The mechanism of inhibition by 2,2'-pyridylisatogen tosylate of NADPH-linked enzyme activities in microsomes isolated from rat liver. 299 19

Sonic disrupted mitoplasts from 3-methylcholanthrene (MCA) treated rats can catalyze the formation of benzo(a)pyrene (BaP) adducts with calf thymus DNA in the presence of an NADPH generating system. The mitoplasts used in this study contained less than 1% microsomal marker enzymes: rotenone insensitive NADPH cytochrome c reductase and glucose-6-phosphatase. The rates of BaP metabolism and DNA adduct formation per nanomole cytochrome P-450 were different for MCA induced mitochondrial and microsomal enzymes. The major B(a)P DNA adducts formed in incubations with lysed mitoplasts were derived from reaction of 9-OH-B(a)P-4,5 oxide with deoxyguanosine. The results suggest a potential role of mitochondrial monooxygenase activity in the covalent binding of B(a)P to mitochondrial DNA.
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PMID:Formation of benzo(alpha)pyrene metabolites and DNA adducts catalyzed by a rat liver mitochondrial monooxygenase system. 299 32

Human lung cancer cell lines in culture were investigated for the expression of monooxygenase and other xenobiotic-metabolizing enzyme activities. Two bronchiolo-alveolar carcinoma derived cell lines (NCI-H322 and NCI-H358) and two small-cell carcinoma derived cell lines (NCI-H128 and NCI-H69) were used. Previous work has shown that NCI-H322 has ultrastructural features of Clara cells while NCI-H358 shows characteristics of alveolar type II cells [Schuller et al., Proc. Am. Ass. Cancer Res. 26, 27 (1985)]. NCI-H128 and NCI-H69 show very poor differentiation of cytoplasmic organelles. Cytochrome P-450 levels were spectroscopically detectable only in NCI-H322. Both NCI-H322 and NCI-H358, but not NCI-H69 and NCI-H128, exhibited aryl hydrocarbon hydroxylase (using benzo[a] pyrene as substrate) and ethoxycoumarin O-deethylase activities. These activities were highly inducible following pretreatment with the polycyclic aromatic hydrocarbons (PAH) beta-naphthoflavone or benzo[a] anthracene. The PAH produced a 2-fold increase in spectroscopically detectable cytochrome P-450 levels in NCI-H322. Following induction, cytochrome P-450 was also spectroscopically detectable in NCI-H358. No aldrin epoxidase activity was present in either untreated or pretreated cell lines. Pretreatment with phenobarbitone or dexamethasone did not induce the aryl hydrocarbon hydroxylase activity in either NCI-H322 or NCI-H358. The ethoxycoumarin O-deethylase activity in beta-naphthoflavone-pretreated NCI-H322 and NCI-H358 was inhibited in a concentration-dependent manner by ellipticine, alpha-naphthoflavone, cimetidine or metyrapone. Untreated NCI-H322 and NCI-H358 also contained cytochrome b5, NADPH cytochrome c reductase and epoxide hydrolase activities. None of these enzyme activities measured was detectable in the untreated or pretreated small-cell derived cancer cell lines (NCI-H128 and NCI-H69). These data show that the two bronchiolo-alveolar carcinoma derived cell lines (NCI-H322 and NCI-H358) exhibit cytochrome P-448-dependent monooxygenase activity and may thus prove useful to study the processes of xenobiotic activation in human lung.
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PMID:Xenobiotic-metabolizing enzyme activity in human non-small-cell derived lung cancer cell lines. 300 5

Male Wistar rats were exposed to 0.4, 1.2, and 4.0 ppm nitrogen dioxide (NO2) for up to 14 weeks to examine subacute effects of NO2 on membrane constituents of lung, liver, and kidney. In the lung, cytochrome P-450 decreased to 59% (P less than 0.01) and 57% (P less than 0.01) of the control values after 1 and 10 weeks of exposure to 4.0 ppm NO2, respectively, and remained at control levels at other exposure periods. The activity of succinate-cytochrome c reductase also decreased to 75% (P less than 0.01) of the control values after 2, 4, and 14 weeks of exposure to 4.0 ppm NO2, respectively. Exposures to 0.4 and 1.2 ppm NO2 resulted in similar patterns of alterations in these enzymes. In the liver, cytochrome P-450 decreased to 72% (P less than 0.01), 70% (P less than 0.05), and 73% (P less than 0.05) of the control values after 1, 5, and 8 weeks of exposure to 4.0 ppm NO2, respectively, and remained at control levels at other exposure periods. The activity of NADPH-cytochrome P-450 reductase also decreased in a fashion similar to cytochrome P-450. Exposures to 0.4 and 1.2 ppm NO2 resulted in similar patterns of alterations in these enzymes. In addition, cytochrome b5 showed a reduced value between 5 and 12 weeks of exposures to 1.2 and 4.0 ppm NO2 and then recovered. In the kidney, all components of the microsomal electron-transport systems increased during 12-week exposures to 1.2 and 4.0 ppm NO2. These results show that subacute exposures to 0.4-4.0 ppm NO2 caused a periodic reduction in microsomal cytochrome P-450 and mitochondrial succinate-cytochrome c reductase in the lung and in components of the microsomal electron-transport systems in the liver, whereas exposures to 1.2 and 4.0 ppm NO2 resulted in induction of the microsomal electron-transport systems in the kidney.
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PMID:Subacute effects of nitrogen dioxide on membrane constituents of lung, liver, and kidney of rats. 301 57

Therapy with enzyme inducing drugs may improve glycemic control in patients with non-insulin-dependent diabetes mellitus. We evaluated the role of a mixed function oxidase system on glucose metabolism with an animal model. Rats were treated with an inducer (phenobarbital), an inhibitor (cimetidine) and a hepatotoxin (carbon tetrachloride) for a week to cause alterations in the liver. The mixed function oxidase system was assayed by determination of the cytochrome P-450 content and NADPH cytochrome c reductase in liver. Carbohydrate metabolism was evaluated by determining blood glucose, enzymes associated with glucose phosphorylation in the liver (glucokinase, hexokinase), glucose storage as glycogen and enzymatic delivery, glucose-6-phosphatase, and peripheral tissue by determining phosphorylating enzyme (hexokinase) and a key glycolytic enzyme (pyruvate kinase) and glycogen content in muscles. The therapy with the inducer enhanced glucose utilization in liver and storage in muscles. The inhibitor decreased the mixed function oxidase system, reduced glucose phosphorylating, but not gluconeogenetic enzymes, in the liver and increased glycolysis in muscles. Carbon tetrachloride, a hepatotoxin, impaired mixed function oxidase, glucose phosphorylating and delivering enzyme activity in liver, reduced blood glucose and caused glycogen accumulation in muscles. The function of liver microsomal enzyme system seems to be closely related to enzymatic glucose metabolism in the liver and muscles.
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PMID:Hepatic mixed function oxidase system and enzymatic glucose metabolism in rats. 304 Mar 22

Specific polyclonal antibodies were used to investigate the distribution of two cytochrome P-450 isozymes (5 and 8), NADPH cytochrome c reductase, and epoxide hydrolase in adult human hepatocytes cultured alone or co-cultured with rat liver epithelial cells. The enzymes were localized by the indirect immunoperoxidase technique following fixation with a paraformaldehyde-glutaraldehyde mixture and membrane permeabilization with saponin. The pattern of distribution of the four enzymes after 24 hr in culture was similar to that found in vivo. Virtually all the hepatocytes exhibited nearly homogeneous positive staining for cytochrome P-450-8, whereas only 60-80% were positive for cytochrome P-450-5. Nearly homogeneous staining was also observed in all hepatocytes for NADPH cytochrome c reductase and epoxide hydrolase. During the first 12 days in pure culture, the intensity of staining, as well as the number of positively stained cells, decreased slightly except for epoxide hydrolase, which did not show any obvious change. In contrast, even after 15 days in co-culture the extent of staining for all the enzymes decreased less than in pure culture. These results indicate that adult human hepatocytes continue to express specific drug-metabolizing enzymes for several days in culture and provide further evidence that those cells are more stable than rodent hepatocytes in primary culture.
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PMID:Immunocytochemical evidence for the maintenance of cytochrome P-450 isozymes, NADPH cytochrome C reductase, and epoxide hydrolase in pure and mixed primary cultures of adult human hepatocytes. 308 26

A unique cytochrome P-450-dependent fatty acid monooxygenase from Bacillus megaterium ATCC 14581 is strongly induced by phenobarbital (Narhi, L. O., and Fulco, A. J. (1982) J. Biol. Chem. 257, 2147-2150) and many other barbiturates (Kim, B.-H., and Fulco, A. J. (1983) Biochem. Biophys. Res. Commun. 116, 843-850). This monooxygenase has now been purified to homogeneity from pentobarbital-induced bacteria as a single polypeptide with a molecular weight of 119,000 +/- 5,000 daltons. In the presence of NADPH and O2, it can catalyze the oxygenation of long chain fatty acids without the aid of any other protein. The enzyme has a catalytic center activity of 4,600 nmol of fatty acid oxygenated per nmol of P-450 (the highest activity yet reported for a P-450-dependent monooxygenase) and also functions as a highly active cytochrome c reductase in the presence of NADPH. The purified holoenzyme is a soluble protein containing 40 mol % hydrophobic amino acid residues and 1 mol each of FAD and FMN/mol of heme. It is isolated and purified in the low spin form but is converted to the high spin form in the presence of long chain fatty acids. The enzyme, which catalyzes the omega-2 hydroxylation of saturated fatty acids and the hydroxylation and epoxidation of unsaturated fatty acids has its highest affinity (Km = 2 +/- 1 microM) for the C15 and C16 chain lengths.
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PMID:Characterization of a catalytically self-sufficient 119,000-dalton cytochrome P-450 monooxygenase induced by barbiturates in Bacillus megaterium. 308 9

The administration of xenobiotics such as phenobarbital (PB) and chlorinated hydrocarbons to rats, mice and several other species has been shown to increase the level of hepatic mixed function oxidases. Experiments were conducted to establish the effect of dose of PB, sex of animals, and effect of interval from dose to measurement on concentration of hepatic enzymes in barrows and gilts 6 to 9 mo of age and weighing 100 to 120 kg. Animals given 1 or 2 g PB for 3 d had higher concentrations of microsomal protein cytochrome b5 and P-450 and NADPH cytochrome c reductase than control animals (P less than .01). Animals given 2 g PB had 3.5 times as much cytochrome P 450 as did controls. Barrows and gilts did not differ from each other in any variables measured (P less than .20). In a study of the time course of induction all animals given PB had higher levels of microsomal protein, cytochrome P-450 and reductase in 24 h than controls; however, cytochrome b5 was depressed on d 1 and was elevated by d 3. Concentration of cytochrome P-450 reached a maximum by d 7 (P less than .01); cytochromes b5 and c reductase reached a maximum by d 9 and 3, respectively (P less than .01). Levels of cytochrome P-450 were higher in gilts than in barrows on all days following PB treatment (P less than .04). Microsomal protein, cytochrome b5, cytochrome P-450 and reductase remained elevated for 6 d after the last treatment with PB.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The influence of dose of phenobarbital and interval to measurement on concentration of liver enzymes in barrows and gilts. 309 95


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