Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibitors of mammalian cytochrome P450 and P450 reductase were used to investigate the enzymes in flounder (Platichthys flesus) hepatic microsomes involved in the stimulation of NAD(P)H-dependent iron/EDTA-mediated 2-keto-4-methiolbutyric acid (KMBA) oxidation (hydroxyl radical production) by the redox cycling compounds menadione and nitrofurantoin. Inhibitors were first tested for their effects on flounder microsomal P450 and flavoprotein reductase activities. Ellipticine gave type II difference binding spectra (app. Ks 5.36 microM; delta A max 0.16 nmol-1 P450) and markedly inhibited NADPH-cytochrome c reductase, NADPH-cytochrome P450 reductase, and monooxygenase (benzo[a]pyrene metabolism) activities. 3-aminopyridine adenine dinucleotide phosphate (AADP; competitive inhibitor of P450 reductase) inhibited NADPH-cytochrome c but not NADH-cytochrome c or NADH-ferricyanide reductase activities. Alkaline phosphatase (inhibitor of rabbit P450 reductase) stimulated NADPH-cytochrome c reductase activity seven fold but had less effect on NADH-reductase activities. AADP inhibited nitrofurantoin- and menadione-stimulated KMBA oxidation by 45 and 17%, respectively, indicating the involvement of P450 reductase at least in the former. In contrast, ellipticine had relatively little effect, possibly because, unlike cytochrome c, the smaller xenobiotic molecules can access the hydrophilic binding site of P450 reductase. Alkaline phosphatase stimulated NAD(P)H-dependent basal and xenobiotic-stimulated KMBA oxidation, showing general consistency with the results for reductase activities. Overall, the studies indicate both similarities (ellipticine, AADP) and differences (alkaline phosphatase) between the flounder and rat hepatic microsomal enzyme systems.
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PMID:Inhibition studies on the involvement of flavoprotein reductases in menadione- and nitrofurantoin-stimulated oxyradical production by hepatic microsomes of flounder (Platichthys flesus). 807 49

Glycosyl-phosphatidylinositol-anchored membrane proteins (GPI-proteins) are normally identified either by cleavage of the lipid anchor using (glycosyl)phosphatidylinositol-specific phospholipases C or D (GPI-PLs) or by metabolic labeling of the lipid moiety with specific building blocks. Therefore, methods for discrimination between transmembrane proteins and GPI-proteins on the basis of their physicochemical properties are desirable. Here we are presenting a selective extraction method for typical well-characterized mammalian GPI-proteins, e.g., acetylcholine esterase, alkaline phosphatase, 5'-nucleotidase, and lipoprotein lipase, using a derivative of taurocholate. The results were compared to those obtained with well-characterized transmembrane proteins, e.g., insulin receptor and hydroxymethyl glutaryl coenzyme A-reductase, glucose transporters, or aminopeptidase M and several commercially available detergents. With regard to total membrane proteins, it was possible to selectively enrich GPI-proteins up to 8- to 14-fold by using concentrations between 0.1 and 0.3% of 4'-NH2-amino-7 beta-benzamido-taurocholic acid (BATC). In addition, the cleavage specificity and efficiency of (G)PI-PLs were increased in the presence of identical concentrations of BATC compared to commonly used detergents, e.g., Nonidet P-40. Therefore, the present study shows that the use of BATC facilitates the identification of glycosyl-phosphatidylinositol-anchored membrane proteins.
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PMID:4'-Amino-benzamido-taurocholic acid selectively solubilizes glycosyl-phosphatidylinositol-anchored membrane proteins and improves lipolytic cleavage of their membrane anchors by specific phospholipases. 813 45

Compared to prior studies which frequently pinpoint the impairment of one parameter or function, this paper reports for the first time an extensive characterization of the toxic effects of gentamicin in a single model of primary cultured rabbit proximal tubule cells developed without insulin and glucose. Biochemical, functional and morphological approaches were used. Cellular response pattern was examined after a 72-h exposure during either the exponential growth phase or the stationary confluency phase of the culture to 0.2, 1, and 2.5 mM gentamicin. The biochemical study after gentamicin exposure showed increased activities for N-acetyl-beta-D-glucosaminidase and alkaline phosphatase, decreased activities for sphingomyelinase, cathepsin B, Na+/K(+)-ATPase, lactate dehydrogenase and NADPH cytochrome C reductase. Functional evaluation revealed decreased protein synthesis and alpha-methylglucose transport after gentamicin exposure. Morphometric study made it possible to show that the density of lysosomes, the cell fractional volume of the lysosomal compartment, and the mean size of the lysosomal profiles are increased in the cells. Intracellular accumulation of gentamicin in proximal tubular cells was dose dependent and reached high levels in cultured cells. In conclusion, this model compared to others in the literature allowed us to demonstrate in vitro a close response pattern to the in vivo situation after gentamicin exposure.
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PMID:Characterization of gentamicin-induced dysfunctions in vitro: the use of optimized primary cultures of rabbit proximal tubule cells. 821 May 60

The terminal electron transfer enzyme Me2SO reductase of Escherichia coli is a heterotrimeric enzyme composed of a membrane extrinsic catalytic dimer (DmsAB) and a membrane intrinsic polytopic anchor subunit (DmsC). The topology of DmsC has been studied using phoA (alkaline phosphatase) and blaM (beta-lactamase) gene fusions. The results of analyzing the properties of proteins produced by the fusions suggests a structure with eight transmembrane helices. Both the amino and carboxyl termini are exposed to the periplasm. The entire DmsC polypeptide is necessary to anchor DmsAB to the membrane as fusions with truncated DmsC were not functional and soluble DmsAB accumulated in the cytoplasm. A dmsC-phoA fusion in the termination codon of dmsC generated a chimeric enzyme with functional Me2SO reductase and alkaline phosphatase activity. Quantitation of the minimal inhibitory concentration of ampicillin for the dmsC-blaM fusions indicated that different transmembrane helices had differing signal sequence activity.
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PMID:The topology of the anchor subunit of dimethyl sulfoxide reductase of Escherichia coli. 842 2

The toxicity of atorvastatin (AT), an inhibitor of hydroxymethylglutaryl-coenzyme A reductase (HMG), was evaluated in beagle dogs. In 4 studies [2-wk rising dose (daily increasing doses for 1 wk; maintenance for 1 wk), 12-wk rising dose (daily dosing with weekly increases in dose), 2-wk toxicity (daily dosing for 2 wk; 3 dose levels), 13-wk toxicity (daily dosing for 13 wk; 3 dose levels)], dogs received up to 400 mg/kg orally. Doses of 180 mg/kg induced moribundity, necessitating euthanasia. Weight losses up to 26% were seen at doses > or = 150 mg/kg. Decreases in cholesterol levels were dose-related. Alanine and/or aspartate aminotransferase were increased at doses > or = 80 mg/kg; alkaline phosphatase was increased at doses > or = 150 mg/kg. Histopathologic findings were seen at > or = 150 mg/kg and included hepatocellular eosinophilia related to increased smooth endoplasmic reticulum and cholangiohepatitis and cholecystitis at 150 mg/kg in the 2-wk toxicity study; hepatocellular degeneration, centrilobular bridging, cholecystitis, hemorrhage in gallbladder and brain, demyelination of optic nerve, and skeletal muscle necrosis at > or = 280 mg/kg in the 12-wk rising dose study; and erosion and hemorrhage in large intestine, hepatocellular degeneration and necrosis, and inflammation and necrosis of gallbladder epithelium at 320 mg/kg in the 2-wk rising dose study. Doses up to 80 mg/kg for 13 wk did not induce histopathologic lesions in examined organs. AT effectively lowered serum cholesterol in normal lipidemic dogs. Toxicity at AT in dogs was similar to that with other inhibitors of HMG except that lenticular changes were not seen, significant hepatic, testicular, or neurological toxicity was associated only with high doses at AT, and skeletal muscle changes similar to those described in rats and rabbits were identified.
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PMID:Subchronic toxicity of atorvastatin, a hydroxymethylglutaryl-coenzyme A reductase inhibitor, in beagle dogs. 886 88

Human CYP17 (P-450(17alpha), 17alpha-hydroxylase-17,20-lyase)-catalysed side-chain cleavage of 17alpha-hydroxyprogestogens into androgens is greatly dependent on the presence of cytochrome b5. The native form of cytochrome b5 is composed of a globular core, residues 1-98, followed by a membrane insertable C-terminal tail, residues 99-133. In the present study the abilities of five different forms of cytochrome b5 to support the side-chain cleavage activity of CYP17 were compared. The five derivatives were: the native pig cytochrome b5 (native pig), its genetically engineered rat counterpart (core-tail), the soluble core form of the latter (core), the core with the secretory signal sequence of alkaline phosphatase appended to its N-terminal (signal-core) and the latter containing the C-terminal tail of the native rat protein (signal-core-tail). When examined by Edman degradation and MS, the engineered proteins were shown to have the expected N-terminal amino acid sequences and molecular masses. The native pig was found to be acetylated at the N-terminal. The native pig and core-tail enzymes were equally efficient at enhancing the side-chain cleavage activity of human CYP17 and the signal-core-tail was 55% as efficient. The core and signal-core constructs were completely inactive in the aforementioned reaction. All the five derivatives were reduced to varying degrees by NADPH:cytochrome P-450 (NADPH-P450) reductase and the relative efficiencies of this reduction were reminiscent of the behaviour of these derivatives in supporting the side-chain cleavage reaction. In the side-chain cleavage assay, however, NADPH-P450 reductase was used in large excess so that the reduction of cytochrome b5 derivatives was not rate-limiting. The results highlight that productive interaction between cytochrome b5 and CYP17 is governed not only by the presence of a membrane insertable hydrophobic region on the cytochrome b5 but also by its defined spatial orientation at the C-terminal.
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PMID:Interaction of human CYP17 (P-450(17alpha), 17alpha-hydroxylase-17,20-lyase) with cytochrome b5: importance of the orientation of the hydrophobic domain of cytochrome b5. 903 76

Androgens stimulate bone formation and play an important role in the maintenance of bone mass. Clinical observations suggest that both gonadal and adrenal androgens contribute to the positive impact of androgenic steroids on bone metabolism. We investigated the mechanism of action of the adrenal androgen dehydroepiandrosterone (DHEA) and its sulfated compound dehydroepiandrosterone sulfate (DHEAS) on human osteoblastic cells (HOCs) in vitro. The DHEA- and DHEAS-induced effects were analyzed in parallel with the actions elicited by the gonadal androgen dihydrotestosterone (DHT). There was no qualitative difference between the effects of gonadal and adrenal androgens on HOC metabolism in vitro. Both were stimulatory as regards cell proliferation and differentiated functions, but the gonadal androgen DHT was significantly more potent than DHEA. The actions of DHT and DHEA on HOC proliferation and alkaline phosphatase (ALP) production could be prevented by the androgen receptor antagonist hydroxyflutamide and inhibitory transforming growth factor beta antibodies (TGF-beta ab), respectively, but were not affected by the presence of the 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) and 5-alpha-reductase (5-AR) inhibitor 17 beta-N,N-diethylcarbamoyl-4-methyl- 4aza-5 alpha-androstan-3-one (4-MA). This indicates that DHT and DHEA (1) exert their mitogenic effects by androgen receptor-mediated mechanisms, (2) stimulate ALP production by increased TGF-beta expression, (3) that the action of DHT is not affected by the presence of 4-MA, and that (4) DHEA does not need to be metabolized by 3 beta HSD or 5-AR first to exert its effects on HOCs in vitro.
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PMID:Gonadal and adrenal androgens are potent regulators of human bone cell metabolism in vitro. 907 90

Sexually mature female Wistar rats were given daily intragastric doses of ethinylestradiol (EE) and levonorgestrel (LE) used normally in women: (1) 0.03 mg EE and 0.05 mg LE; (2) 0.04 mg EE and 0.075 mg LE; (3) 0.03 mg EE and 0.125 mg LE. All groups were treated for 6 months in 5-day cycles (four-day treatment with a one-day break), i.e. for 36 sexual cycles. In rat kidneys, the activity of succinic dehydrogenase, NADPH-tetrazolium reductase, Mg(2+)-ATPase and alkaline phosphatase were decreased, while those of lactate dehydrogenase, acid phosphatase and glucose-6-phosphatase were enhanced. We have found a correlation between enzymatic changes and ultrastructural changes in epithelial renal cells. These changes may reflect: (1) inhibited oxidative processes associated with the mitochondrial and microsomal systems of electron transport; (2) a compensatory increase in anaerobic processes; (3) increased glyconeogenesis; (4) inhibited transport processes and increased cellular catabolism. The kidney cortex and medulla did not show any significant morphological changes after 6 months of treatment. The study has shown that EE/LE combinations produce histochemical and ultrastructural changes in the kidney, which are dependent on the doses of gestagens.
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PMID:Effects of ethinylestradiol and levonorgestrel on morphology, ultrastructure and histoenzymatic activity of rat kidney. 980 70

The mechanism for the catalytic reduction of the double bond at C-7, 8 in 7-dehydrocholesterol by 3beta-hydroxysterol Delta7-reductase was investigated by testing structurally related sterols as substrates and potential inhibitors. The hepatic smooth endoplasmic reticulum was identified as the site of enzyme activity. All putative substrates contained 27 carbons, but differed from 7-dehydrocholesterol by the addition of either an ethyl substituent at C-24 (7-dehydrositosterol), a double bond at C-22 with a methyl substituent at C-24 (ergosterol), epimerization of the hydroxyl from the 3beta- to 3alpha-configuration (7-dehydroepicholesterol), or a saturated double bond at C-5,6 (lathosterol). Two non-steroidal compounds that inhibit 3beta-hydroxysterol Delta7-reductase in vivo (AY 9944 and BM 15.766) were also tested. Ergosterol, 7-dehydrositosterol, and 7-dehydroepicholesterol were reduced at C-7, 8 to form brassicasterol, sitosterol, and epicholesterol, respectively, but 75% less efficiently than 7-dehydrocholesterol. Increasing concentrations of these sterols competitively inhibited 3beta-hydroxysterol Delta7-reductase activity. The double bond at C-7,8 in lathosterol was not reduced. AY 9944 and BM 15.766 inhibited 3beta-hydroxysterol Delta7-reductase activity non-competitively. 3beta-Hydroxysterol-Delta7-reductase activity declined after microsomes were exposed to alkaline phosphatase, and enzyme activity was increased by phosphorylation with Mg2+, and ATP. These results demonstrate that the reduction of the double bond at C-7,8 requires binding of the enzyme protein with the B-ring of the sterol substrate that contains a double bond at C-5,6. The reaction is hindered by substituents located on the apolar side-chain and epimerization of the hydroxyl group in ring A to a 3alpha-configuration. 3beta-Hydroxysterol Delta7-reductase exists in two forms: an active phosphorylated form and an inactive dephosphorylated form.
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PMID:Regulation of rat hepatic 3beta-hydroxysterol delta7-reductase: substrate specificity, competitive and non-competitive inhibition, and phosphorylation/dephosphorylation. 983 36

The aim of the present study was to investigate whether the brush border membrane ferric reductase activity of Caco-2 cells is modulated during cell differentiation. The ferric reductase activity was determined in whole cells and isolated microvillous membranes at different stages of cell differentiation by measuring the amount of Fe3+ reduced during the incubation time. Our results indicated that the ferric reductase activity decreased in fastly growing cells and reactivated in postconfluent cells in contrast to the alkaline phosphatase and sucrase activities which were progressively expressed during differentiation as conventional indicators of cell maturity. The lowest ferric reductase activity was found in cells at the log phase of proliferation, while freshly seeded or highly differentiated cells had significantly higher enzyme activities. Cells grown under serum-free conditions had similar ferric iron reduction rates as cells propagated under standard conditions. Reagents or hormones affecting cell metabolism through different pathways had no significant effect on this transplasma membrane redox system.
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PMID:The plasma membrane Fe(3+)-reductase activity of Caco-2 cells is modulated during differentiation. 986 49


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