共查询到20条相似文献,搜索用时 31 毫秒
1.
NADPH reduces both liver microsomal cytochrome P-450 and cytochrome . In the presence of CO, ferrous cytochrome P-450 can slowly transfer electrons to amaranth, an azo dye. This reaction is followed by the reoxidation of cytochrome which proceeds at essentially the same rate as does cytochrome P-450 oxidation. It is suggested that cytochrome directly reduces cytochrome P-450 in rat liver microsomes. 相似文献
2.
A gel-electrophoretically homogeneous preparation of cytochrome P-450 from liver microsomes of phenobarbital-pretreated rabbits 总被引:9,自引:0,他引:9
Cytochrome P-450 was purified from liver microsomes of phenobarbital-pretreated rabbits to a specific content of 16 to 17 nmoles per mg of protein with a yield of about 10 %. The purified cytochrome yielded only a single protein band on sodium dodecylsulfate-urea-polyacrylamide gel electrophoresis, and an apparent molecular weight of about 45,000 was estimated for the protein. The preparation was free of cytochrome , NADH-cytochrome reductase, and NADPH-cytochrome reductase activities. Aniline hydroxylase and ethylmorphine N-demethylase activities could be reconstituted upon mixing the purified cytochrome with an NADPH-cytochrome reductase preparation (purified by a detergent method) and phosphatidyl choline. 相似文献
3.
Cytochrome b5 as electron donor to rabbit liver cytochrome P-450LM2 in reconstituted phospholipid vesicles 总被引:3,自引:0,他引:3
M Ingelman-Sundberg I Johansson 《Biochemical and biophysical research communications》1980,97(2):582-586
When incorporated into phospholipid vesicles containing NADPH-cytochrome P-450 reductase and P-450LM2, cytochrome b5 enhanced the rate of NADPH-supported hydroxylation of 7-ethoxycoumarin or -nitroanisole about 5-fold. Cytochrome b5 did not affect the rate of NADPH-oxidation, nor the rate of NADPH-supported formation of the ferrous CO-complex of cytochrome P-450. However, the cytochrome b5-mediated increase in product formation was found to be correlated with concomitant decreases in the production of H2O2 or in the system, thus strongly indicating cytochrome b5 being a more efficient donor of the second electron to cytochrome P-450 than is NADPH-cytochrome P-450 reductase. 相似文献
4.
F. Peter Guengerich David P. Ballou Minor J. Coon 《Biochemical and biophysical research communications》1976,70(3):951-956
Stopped flow spectrophotometry has shown the occurrence of two distinct spectral intermediates in the reaction of oxygen with the reduced form of highly purified cytochrome P-450 from liver microsomes. As indicated by difference spectra, Complex I (with maxima at 430 and 450 nm) is rapidly formed and then decays to form Complex II (with a broad maximum at 440 nm), which resembles the intermediate seen in steady state experiments. In the reaction sequence, P-450LMredComplex I→Complex II→P-450LMox the last step is rate-limiting. The rate of that step is inadequate to account for the known turnover number of the enzyme in benzphetamine hydroxylation unless NADPH-cytochrome P-450 reductase or cytochrome is added. The latter protein does not appear to function as an electron carrier in this process. 相似文献
5.
Highly purified divalent and monovalent antibodies against cytochrome , anti- immunoglobulin G (IG) and anti- Fab', were used in elucidating the role of this cytochrome in the drug-oxidizing enzyme system of mouse liver microsomes. Anti- IG strongly inhibited not only NADH-supported but also NADPH-supported oxidation of 7-ethoxycoumarin and benzo(a)pyrene, but had no inhibitory action on the oxidation of aniline. Anti- Fab' also inhibited NADH-supported and NADPH-supported benzo(a)pyrene hydroxylation. These observations indicate an essential role of cytochrome in the transfer of electrons not only from NADH but also from NADPH to cytochrome P-450 in the microsomal oxidation of some drugs, but not of aniline. 相似文献
6.
Yoshiyuki Ichikawa 《生物化学与生物物理学报:生物膜》1975,394(3):406-415
Optical and magnetic studies were made on subfractions of rabbit kidney cortex. Cytochrome and cytochrome mixed function oxidase systems were localized mainly in the brush border membranes and microsomes. Cytochrome mixed function oxidases in the membranes comprised both an NADPH-dependent system and an NADH-dependent system. 相似文献
7.
J L Purvis J A Canick S A Latif J H Rosenbaum J Hologgitas R H Menard 《Archives of biochemistry and biophysics》1973,159(1):39-49
The lifetime of different microsomal steroidogenic enzymes and the cytochrome components of the NADPH-cytochrome P-450 pathway have been determined in rat testis by measuring their decrease logarithmically after hypophysectomy. Although both cytochrome P-450 and 17α-hydroxylase show biphasic decay curves, the first decay curve contains 89–94% of the cytochrome P-450 and 17α-hydroxylase levels. Steroidogenic enzymes which are located mainly in the leydig cells, decay much faster than microsomal protein, days, which represents mainly decay of tubular protein. The similarity between the major half-life of cytochrome P-450, days, 17α-hydroxylase, days and the C17–C20 lyase, days and the uniformity of their response to human chorionic gonadotrophin (HCG) provides additional evidence that these two steroidogenic enzymes require cytochrome P-450. Both the 17α-hydroxylase and the C17–C20 lyase were shown to have a constant activity per nmole of cytochrome P-450 during a sixfold change in the level of cytochrome P-450 brought about by HCG treatment of rats with intact pituitaries. The decay of 17β-hydroxysteroid dehydrogenase, days, was slower than P-450 dependent enzymes. Rats with intact pituitaries are not under maximal stimulation by endogenous LH because addition of HCG increases the levels of microsomal and mitochondrial cytochrome P-450 220 and 1620%, respectively. The rates of synthesis during the increase from one cytochrome P-450 level to another was calculated at testes/day for microsomal cytochrome P-450 and 0.10 nmoles/2 testes/day for mitochondrial cytochrome P-450. Treatment of hypophysectomized rats with HCG results in large increases of cytochrome P-450, 17α-hydroxylase, C17–C20 lyase and 5α-reductase, but not cytochrome b5, microsomal protein, 7α-hydroxylase, or the 17β-hydroxysteroid dehydrogenase. While it is clear that the two cytochrome P-450 dependent hydroxylases involved in steroidogenesis and the 5α-reductase are under the control of gonadotrophin, it is not clear how 17β-hydroxysteroid dehydrogenase levels are maintained or in what manner the 5α-reductase level is controlled in mature animals. 相似文献
8.
The role of cytochrome 5 in the -nitroanisole O-demethylation was studied with a reconstituted system containing a unique cytochrome P-450, isolated from rabbit liver microsomes as a species with a high affinity for cytochrome 5. The maximal activity was obtained in the complete system consisting of cytochrome P-450, NADPH-cytochrome P-450 reductase, NADH-cytochrome 5 reductase, and Triton X-100 in addition to cytochrome 5. The omission of cytochrome 5 from the complete system entirely abolished the activity. These results clearly show that cytochrome 5 is obligatory in the reconstitute p-nitroanisole O-demethylation system, and this cytochrome P-450 probably interacts with cytochrome 5 in such a way that the second electron is transferred from cytochrome 5 and thus exhibits the demethylase activity. 相似文献
9.
The cytochrome reductase system solubilized from microsomes exhibits monophasic reduction kinetics over the temperature range 15 ° to ?25 °C in aqueous/ethylene glycol co-solvent, whereas in intact microsomes, the process becomes increasingly heterogeneous below 0 °C, reflecting heterogeneities in membrane structure observable as distributions in reaction rates and activation energies. 相似文献
10.
Bengt Jernström Jorge Capdevila Sten Jakobsson Sten Orrenius 《Biochemical and biophysical research communications》1975,64(3):814-822
Cytochrome P-450 from rat lung microsomes has been solubilized and purified 8-fold by using affinity chromatography on an ω-amino--octyl derivative of Sepharose 4B. The purified fraction was free of cytochrome 5 and NADPH-cytochrome reductase and showed spectral characteristics similar to those of lung microsomal cytochrome P-450. When combined with NADPH-cytochrome reductase partially purified from liver microsomes, the cytochrome P-450 fraction supported the hydroxylation of benzo (α)pyrene and the activity was proportional to the content of the hemoprotein. No absolute requirement for phosphatidylcholine was found. 相似文献
11.
Both the cytochrome b5 level and NADH cytochrome b5 reductase activity in rat liver microsomes were increased 2-fold by repeated i.p. administration of 1.5 mmol/kg propylthiouracil (PTU) for 2 weeks, but neither the cytochrome P-450 level nor NADPH cytochrome P-450 reductase activity were affected by the treatment. Liver microsomes from PTU-treated rats showed a significant decrease in aminopyrine N-demethylation, but not in benzphetamine N-demethylation, aniline hydroxylation or 7-ethoxycoumarin O-deethylation. A single administration of the compound had no effect on any components of the system. , drug hydroxylation activities were not affected by PTU up to 1.0 mM. From the above evidence, repeated administration of PTU selectively induced cytochrome b5 and NADH cytochrome b5 reductase in rat liver microsomes. 相似文献
12.
José Remacle 《生物化学与生物物理学报:生物膜》1980,597(3):564-576
The in vitro incorporation of cytochrome into purified plasma membranes was investigated by biochemical and immunological methods. Plasma membrane preparations incorporated three times less cytochrome than did microsomal preparations; 60% of this cytochrome could not be reduced by the NADH-cytochrome reductase and was considered as being bound to the plasma membrane. The morphological observations made after the immunochemical labeling of cytochrome clearly showed a good but asymmetrical distribution of the ferritin labeling: only the inner face of the plasma membrane incorporated cytochrome . These results are discussed with respect to theories which concern the subcellular membrane relationships in the cell. 相似文献
13.
Shakunthala Narasimhulu 《生物化学与生物物理学报:生物膜》1979,556(3):457-468
The addition of cholate to the microsomes at 37.5°C resulted in a striking decrease in the apparent substrate dissociation constant () and its temperature dependency. The microsomal membranes depleted of 80% of the lipids preserved the temperature dependency of the and exhibited breaks in the Van't Hoff plot at the characteristic temperature of the lipids phase transition. The results indicate that the cytochrome is considerably restrained from expressing its maximum substrate binding potential at physiological temperature. In addition, the results indicate that the majority of the lipids apparently do not play a significant role in imposing constraint on the substratecytochrome binding reaction and in the temperature dependency of the . 相似文献
14.
Dorothy A. Schafer Donald E. Hultquist 《Biochemical and biophysical research communications》1980,95(1):381-387
Microsomal NADH-cytochrome reductase has been purified from bovine liver by an improved procedure which employs affinity chromatography on ADP-agarose in combination with anion exchange chromatography. The reductase was extracted from a 105,000 × microsomal pellet with Triton X-100. The overall purification from isolated microsomes was 98-fold and the yield was 10%. The preparation was nearly homogeneous on SDS-PAGE. This procedure requires less time and effort than previously described procedures. Partially purified cytochrome is also obtained. 相似文献
15.
K M Ivanetich I Aronson I D Katz 《Biochemical and biophysical research communications》1977,74(4):1411-1418
In the presence of hepatic microsomes, vinyl chloride produces a ‘type I’ difference spectrum and stimulates carbon monoxide inhibitable NADPH consumption. A comparison of the binding and Michaelis parameters for the interaction of vinyl chloride with uninduced, phenobarbital and 3-methylcholanthrene induced microsomes indicates that the binding and metabolism of vinyl chloride is catalyzed by more than one type P-450 cytochrome, but predominantly by cytochrome P-450. Metabolites of vinyl chloride from this enzyme system decrease the levels of cytochrome P-450 and microsomal heme, but not cytochrome 5 or NADPH-cytochrome reductase . 相似文献
16.
The adaptation of a commercially available dual wavelength/stopped flow spectrophotometer for use with turbid samples is described. A minicomputer is used to collect and analyze the data, thereby facilitating these experiments. The stopped flow/computer combination has a dead time in the single wavelength mode of 3.5 msec. In the dual wavelength mode, accurate determinations can be made of the time course of reactions that have a of 50 msec or longer. The application of this stopped flow spectrophotometer to the measurement of cytochrome P-450 reductase activity in rat liver microsomes is described. 相似文献
17.
Ubisemiquinone radicals from the cytochrome b-c1 complex of the mitochondrial electron transport chain--demonstration of QP-S radical formation 总被引:2,自引:0,他引:2
Y Wei C P Scholes T E King 《Biochemical and biophysical research communications》1981,99(4):1411-1419
Stable ubisemiquinone radical(s) in the cytochrome -II complex of bovine heart was observed following reduction by succinate in the presence of catalytic amounts of succinate dehydrogenase. The radical was abolished by addition of antimycin A, but a residual radical remained in the presence of excess exogenous Q2. The radical showed an EPR signal of g = 2.0046 ± .003 at X band (~9.4 GHz) with no resolved hyperfine structure and had a line width of 8.1 ± .5 Gauss at 23°C. The Q band (35 GHz) spectra showed wellresolved -anisotropy and had a field separation between derivative extrema of 26 ± 1 Gauss. This radical is evidently from QP-C. These observations substantiate that the radical is immobilized and bound to a protein. The QP-S radical was demonstrated in the cytochrome -II complex only in the presence of more than a catalytic amount of succinate dehydrogenase and cytochrome . This signal was not antimycin a inhibitory. The signal amplitude paralleled the reconstitutive enzymic activity of succinate-cytochrome reductase from succinate dehydrogenase and the cytochrome -II complex. 相似文献
18.
B L Trumpower 《Biochemical and biophysical research communications》1976,70(1):73-80
A protein named oxidation factor can be reversibly removed from succinate-cytochrome reductase complex and shown to be required for electron transfer between succinate and cytochrome . This protein is required for reduction of cytochrome and, in the presence of antimycin, for reduction of both cytochromes and . These results are consistent with a protonmotive Q cycle mechanism in which the oxidation factor catalyzes electron transfer from reduced quinone to cytochrome and thus liberates from reduced quinone one of two protons required for energy conservation during electron transfer through the cytochrome complex. 相似文献
19.
The association of fatty acids, androstane, phosphatidylcholine, phosphatidylethanolamine, and phosphatidic acid with purified and phospholipid-vesicle reconstituted cytochrome was studied by spin labeling. Spin-labeled fatty acids were found to be motionally restricted by cytochrome in both phospholipid vesicles and in microsomes to a much greater extent than spin-labeled phospholipids. The equilibrium of spin-labeled fatty acid between the bulk membrane lipid and the protein interface could be shifted towards an increased amount in the bulk phospholipid phase by the addition of oleic acid or lysophosphatidylcholine, but not by sodium cholate. Microsomes from different animals showed a variable extent of motional restriction of fatty acids, independent of pretreatment of the animals with phenobarbital or β-naphthoflavone, of cytochrome content, of the presence of type I and type II substrates for cytochrome . These differences are attributed to the presence of varying amounts of lipid breakdown products in the microsomal membrane such as lysolipids or fatty acids which compete with the externally added spin-labeled fatty acids, or with spin-labeled androstane for the binding to cytochrome . The negative charge of the fatty acid was found to be involved in its association with the protein. Cytochrome was shown to interact only with a few spin-labeled phospholipid molecules in such a way that the motional restriction of the spin acyl chains can be detected by electron paramagnetic resonance (). The number of associated lipid molecules per protein probably is too small to form a complete shell around the protein. This lipid-protein interaction could be destroyed by the addition of sodium cholate, in contrast to the fatty acid-protein interaction. 相似文献
20.
A rat liver nuclear envelope fraction isolated essentially by the technique of Monneron et al. (J. Cell Biol. 55, 104–125 (1972)) is characterized by high levels of glucose-6-phosphatase and 5′-nucleotidase. A broadly specific nucleoside triphosphatase activity is present. Cytochromes and as well as NADPH- and NADH-cytochrome reductase activities are present but at lower levels than found in microsomes. Cytochrome oxidase activity is low. RNA polymerase activity is absent from the nuclear envelope fraction. Cytochemistry shows that glucose-6-phosphatase activity is strong and restricted to the nuclear envelope of nuclei. 5′-Nucleotidase shows weak reaction deposit in whole nuclei but in contrast gives clear reaction deposit in isolated nuclear envelopes. Cytochemical reaction deposit due to nucleoside trisphosphatase activity is not restricted to the nuclear envelope but is found to a larger extent within the nucleus. 相似文献