共查询到20条相似文献,搜索用时 15 毫秒
1.
R J Jackson R M Wolcott T Shiota 《Biochemical and biophysical research communications》1973,51(2):428-435
The conditions for coupling periodate oxidized GTP to a hydrazide Sepharose derivative are described. Approximately 1 μmole of the ligand was bound per milliliter of settled gel. Gel columns prepared from this material bind D-ihydroneopterin triphosphate synthetase, the initial enzyme for folate biosynthesis in . A yield of 28% and an overall enzyme purification of 765 fold were attained when the affinity technique was used with a conventional purification procedure. 相似文献
2.
The possibility that ethanol or acetaldehyde has a direct effect on the activity of acyl-CoA-ligases or -glycerophosphate acyltransferases or on the biosynthesis of phosphatidic acid and triglycerides from free fatty acids was studied with subcellular preparations from rat liver. No stimulatory effect of ethanol or acetaldehyde could be observed in any case. It was further shown that the microsomal fraction of homogenate of livers of rats treated with ethanol (single peroral dose of 4.5 g of ethanol per kg body weight) did not have an increased capacity to biosynthesize phosphatidic acid. The possibility was excluded that excess cofactors necessary for formation of phosphatidic acid are responsible for the higher accumulation of triglycerides in livers of rats treated with ethanol.The results indicate that the increased formation of triglycerides in liver of rats treated with ethanol is not due to increased activity of acyl-CoA-ligase or -glycerophosphate acyltransferase or due to increased availability of -glycerophosphate, ATP or CoA-SH. It is suggested that increased availability of fatty acids is the major explanation for the increased accumulation of triglycerides in the liver after ethanol administration. 相似文献
3.
H A Sasame J R Gillette M R Boyd 《Biochemical and biophysical research communications》1978,84(2):389-395
An antibody prepared against purified rat liver NADPH-cytochrome reductase inhibited both the pulmonary and hepatic microsomal covalent binding of 4-ipomeanol as well as the respective NADPH-cytochrome reductase activities, findings which are consistent with previous studies which indicated the participation of cytochrome P450 in the metabolic activation of the toxin. An antibody prepared against purified rat liver cytochrome b5, which strongly inhibited both the rat hepatic and pulmonary NADH-dependent cytochrome reductases, and was inactive against the respective NADPH-dependent cytochrome reductases, had little effect on metabolic activation of 4-ipomeanol by hepatic microsomes, but strongly inhibited both the NADH-supported and the NADPH-supported pulmonary microsomal metabolism and covalent binding of the compound. These results suggest that metabolic activation of 4-ipomeanol involves a two-electron transfer in which transfer of the second electron via cytochrome b5 is rate-limiting in lung microsomes. 相似文献
4.
The effects of exposure to two types of crude oil on microsomal mixed-function oxidase system components in livers of juvenile striped mullet () were investigated. Mullet were exposed for 4 days to emulsified Empire Mix or Saudi Arabian crude oils at an initial concentration of 75 ppm and an average of 1 ppm in the water column. Liver size was increased by about 50% following exposure to both oils. Since neither total hepatic protein nor microsomal protein increased as rapidly as did liver size, the concentrations of both were reduced following oil exposures. The proportion of microsomal protein to total hepatic protein or wet weight was not altered following crude oil exposure. Both cytochromes P-450 and 5 were induced following oil treatment. NADPH-dependent enzymes assayed with cytochrome and dichlorophenolindophenol as substrates showed increases in activity after exposure to Empire Mix crude oil but only the latter enzyme activity was increased on a microsomal protein basis following Saudi Arabian crude oil treatment. Activities of NADH cytochrome and NADH cytochrome 5 reductases appeared to vary with the protein level. However, since liver size was increased, oil-treated mullet had more of all parameters measured than did control mullet. Although the acute toxicity of Saudi Arabian crude oil to mullet is greater than that of Empire Mix crude oil, Empire Mix crude oil had greater inductive effects on microsomal oxidase components. 相似文献
5.
Man is exposed to epoxides of fatty acids from a number of sources, yet their degradative metabolism is not well understood. In mouse liver the 100,000 g supernatant or the cytosolic fraction is the most active fraction in hydrating - and -epoxymethyl stearates with the oxirane ring opening in a manner to give the corresponding and diols, respectively. Hydration was also observed in the microsomal, nuclei and cell debris, and mitochondrial fractions in decreasing order of specific activity. 相似文献
6.
Rat liver microsomal NADH-cytochrome reductase activity is stimulated by 20 μM thyroxine . Thyroxine does not influence microsomal NADH-dichlorophenolindophenol reductase, NADPH-cytochrome reductase, or NADPH-dichlorophenolindophenol reductase activity. Stimulation of NADH-cytochrome reductase activity is not mediated by super-oxide and is likely due to enhanced reduction or oxidation of cytochrome 5. 相似文献
7.
A.J. Marinello H.L. Gurtoo R.F. Struck B. Paul 《Biochemical and biophysical research communications》1978,83(4):1347-1353
Cyclophosphamide (CP) metabolites, acrolein and 4-hydroxy-CP, were found to denature rat liver microsomal cytochrome P-450, whereas another metabolite, phosphoramide mustard, CP or its analog Ifosfamide had no effect. The denaturation produced by CP metabolites could be blocked by cysteine, suggesting an interaction between CP metabolite(s) and sulfhydryl groups in cysteine and probably in cytochrome P-450. These studies might explain the biochemical basis of the specific depression of various microsomal mixed function oxygenase activities produced by high doses of CP. 相似文献
8.
A method for demonstrating proestrogens has been developed. The method involves the incubation of the potential proestrogen with liver microsomes and NADPH in the presence of rat uteri, followed by examination of the effects of metabolism of the compound on the distribution of uterine estrogen receptor (R) in the cytosol (Rc) and in the nucleus (Rn). Thus, we examined whether DDT derivatives, which possess estrogenic activity , exhibit pro-estrogenic properties . Using this method, it appears that methoxychlor is a proestrogen, since the presence of microsomal enzymatic activity is required for methoxychlor to elicit translocation of uterine Rc into the nucleus, namely, the lowering of Rc and elevation of Rn. By contrast, o,p'DDT was active in translocating Rc and did not require the presence of microsomal enzymes for activity. 相似文献
9.
A highly purified reconstituted system isolated from the microsomes of 3-methylcholanthrene-treated rats consisting of cytochrome P-448, NADPH-cytochrome reductase and synthetic dilauroyl phosphatidylcholine had no DT diaphorase activity, but hydroxylated benzo[a]pyrene at a faster rate than microsomes from 3-methylcholanthrene-treated rats. DT diaphorase purified from liver microsomes of 3-methylcholanthrene-treated rats when added to this reconstituted system did not stimulate or inhibit benzo[a]pyrene hydroxylation, nor could it replace or NADPH-cytochrome reductase in supporting the reaction. We therefore conclude that microsomal DT diaphorase is not involved in microsomal hydroxylation of benzo[a]pyrene to its phenolic products despite the observation that both DT diaphorase activity and the hydroxylation of benzo[a]pyrene are induced by 3-methylcholanthrene and 2,3,7,8-tetrachlorodibenzo--dioxin 相似文献
10.
The from butanol through octanol are membrane perturbing agents that fluidize the microsomal membranes of 20-day-old chick embryo hearts as measured by the fluorescence depolarization of 1,6-diphenylhexatriene. In terms of the aqueous concentrations of the fluidizing effect increases with increasing number of carbons per . In terms of the membrane concentrations of the fluidizing effect is roughly equivalent for all the studied. 相似文献
11.
Dileep S. Sachan Harry P. Broquist 《Biochemical and biophysical research communications》1980,96(2):870-875
An enzyme system in the post mitochondrial fraction of when supplemented with appropriate cofactors formed carnitine from ε-N-trimethyllysine. These findings together with previous studies of ε-N-lysine methylation in this fungi, illustrate that carnitine synthesis in differs markedly in certain features from mammalian systems in that the entire synthesis is carried out employing free intermediates and cytosolic enzymes. 相似文献
12.
Incorporation of C14 Leucine was determined or in isolated mitochondria and microsomes of rat brain and liver after acute or chronic ethanol administration .The protein synthesis in mitochondrial and microsomal preparation was inhibited respectively by chloramphenicol and cycloeximide, specific inhibitors for the two systems tested. The experimental data demonstrate that the protein synthesis in both systems, mitochondrial and microsomal, is strongly affected only after chronic treatment which produces significant activation at the mitochondrial and microsomal level in the liver and an inhibition on the same systems of the brain.The data for protein synthesis instead show strong inhibition after acute administration, except for brain mitochondria, which are practically unaffected, while after chronic treatment no significant alterations are observed. 相似文献
13.
Robert L. Barbieri Rapin Osathanondh Jacob A. Canick Robert J. Stillman Kenneth J. Ryan 《Steroids》1980,35(3):251-263
The effects of danazol on steroidogenesis in the 16–20 week old human fetal adrenal were examined by studying: 1) danazol binding to adrenal microsomal and mitochondrial cytochrome P-450, and 2) enzyme kinetics of danazol inhibition of the adrenal microsomal 21-hydroxylase and the mitochondrial llβ-hydroxylase. The addition of danazol to preparations of adrenal microsomes or mitochondria elicited a type I cytochrome P-450 binding spectrum. Danazol bound to microsomal cytochrome P-450 with a high affinity apparent spectral dissociation constant (Kg) of 1 μM and with a lower affinity K's of 10 μM. Danazol bound to mitochondrial cytochrome P-450 with a Kg of 5 μM. In addition, danazol competitively inhibited the microsomal 21-hydroxylase (apparent enzymatic inhibition constant KI = 0.8 μM) and the mitochondrial 11β-hydroxylase (KI = 3 μM). These findings demonstrate that low concentrations of danazol directly inhibit steroidogenesis in the human fetal adrenal . 相似文献
14.
M.R. Boyd H.A. Sasame R.B. Franklin 《Biochemical and biophysical research communications》1980,93(4):1167-1172
Studies of the ratios of the amounts of 4-ipomeanol covalently bound to the total amounts metabolized support the view that the high rates of pulmonary microsomal alkylation by 4-ipomeanol reflect high rates of NADPH-mediated metabolic activation of the compound rather than a relative deficiency of a microsomal detoxication pathway. Moreover, the ability of 3-methylcholanthene pretreatment, but not phenobarbital pretreatment, to shift the target organ alkylation and toxicity of 4-ipomeanol from the lung to the liver in rats could not be explained by a major alteration in the balances between microsomal toxication and detoxication pathways measurable in the systems examined, nor upon a major change in the nature of the reactive 4-ipomeanol metabolites produced in the lungs or livers of the pretreated animals. 相似文献
15.
The transmembrane electropotential of microsomal vesicles from pea internode segments, monitored by equilibrium distribution of the permeant anion SCN?, is strongly hyperpolarized when ATP is present in the incubation medium.The stimulation of SCN? uptake by ATP is rather specific with respect to the other nucleoside di- and triphosphates tested: ADP, GTP, CTP and UTP. ATP-stimulated SCN? uptake is strongly inhibited by ATPase inhibitors such as and and by 2.5% toluene/ethanol (1 : 4, v/v), the latter being a treatment which makes the vesicles permeable. On the contrary, oligomycin is almost ineffective in influencing ATP-induced SCN? uptake. The proton conductor carbonyl cyanide strongly inhibits ATP-stimulated SCN? uptake. The effect of ATP on SCN? uptake depends on the pH of the medium, the maximum being reached at about pH 7.0.These data support the view that microsomal fractions from pea internodes contain membrane vesicles endowed with a membrane-bound ATPase coupling ATP hydrolysis to electrogenic transport of ions, probably H+. 相似文献
16.
The effect of pretreatment with phenobarbitone, rifampicin, β-naphthoflavone, antipyrine and spironolactone on the irreversible binding of ethynyloestradiol to guinea pig liver microsomes has been examined and the corresponding changes in microsomal P-450 content and cytochrome reductase activity measured. Rifampicin produced the greatest increase (220%) in irreversible binding while phenobarbitone produced the greatest increase in both microsomal P-450 content (172%) and cytochrome reductase activity (210%). There was no correlation of irreversible binding with either microsomal P-450 content or with cytochrome reductase activity. 相似文献
17.
Michael J. Barber Andrew S. Zektzer Gerald M. Rosen Helen A. Demos Elmer J. Rauckman 《生物化学与生物物理学报:生物膜》1984,776(1):159-168
Hepatic microsomal membranes, prepared under various conditions that yield either ‘intact’ or ‘disrupted’ microsomal vesicles, have been labeled via the sulfhydryl groups of intrinsic membrane proteins using nitroxide analogs of . Electron paramagnetic resonance spectra revealed the presence of two dominant classes of bound label corresponding to differing degrees of immobilization, the ratio of which were quantitated using a parameter designated the ‘’ ratio. For latent microsomes, the value of this parameter was determined to be and was influenced by factors such as label/protein ratio, incubation period, nitroxide structure, temperature and pH. The ratio was also sensitive to the degree of membrane integrity as revealed by the latency of mannose 6-phosphate activity of glucose-6-phosphohydrolase. In addition, membrane disruption resulted in a corresponding decrease in the order parameter for nitroxide-labeled fatty acids intercalated within the lipid bilayer. The ratio was observed to be dependent upon the method of microsome preparation yielding values of for ‘hypertonically disrupted’ vesicles and for ‘mechanically disrupted’ vesicles. Microsomal marker enzymes such as cytochrome and FAD-containing monooxygenase retained significant levels of functionally following nitroxide incorporation. 相似文献
18.
Urinary estrone conjugates were measured directly by radioimmunoassay (RIA) in 20 pregnancies from preconception diestrus to day 78 of pregnancy. High performance liquid chromatography separation defined estrone sulfate (ES) as the predominant immunoreactive peak which accounted for 94% to 97% of the total immunoreactivity after chromatography. Diestrous values indexed by creatinine were 0.15 ± 0.07 micrograms/mg Cr, as compared to estrous values which rose to 0.47 ± 0.14 micrograms/mg Cr, . Urinary ES concentrations significantly increased (P = 0.0001 in pregnant mares from day 35 to day 47 (1.21 ± 0.12 micrograms/mg Cr) as compared to day 25 to day 34 (0.27 ± 0.01 micrograms/mg Cr). Measurement of urinary ES may provide an alternate or augmentive method of pregnancy diagnosis in the domestic mare. 相似文献
19.
Selenium and hepatic microsomal hemoproteins 总被引:3,自引:0,他引:3
R F Burk A M Mackinnon F R Simon 《Biochemical and biophysical research communications》1974,56(2):431-436
The microsomal share of liver homogenate 75Se after injection of a tracer dose of 75SeO32? was three times greater in rats fed a selenium-deficient diet than in rats fed a selenium-adequate diet. Basal levels of microsomal cytochromes P-450 and b5 were unaffected by selenium deficiency. However, induction of these cytochromes by phenobarbital was markedly inpaired in selenium-deficient rats, whereas liver weight increase and NADPH cytochrome reductase induction were not impaired. These data indicate that selenium is essential for phenobarbital induction of microsomal hemoproteins. 相似文献
20.
The effect of the dietary antioxidants, vitamin E and selenium, and the effect of phenobarbital pretreatment on NADPH-dependent microsomal lipid peroxidation and the activation of microsomal lipid peroxidation by CCl4 were studied. The rate of microsomal lipid peroxidation decreased as a function of dietary anti-oxidant, while the degree of CCl4 activation increased. Phenobarbital pretreatment diminished the antioxidant inhibition of microsomal lipid peroxidation found with microsomes from rats fed high levels of antioxidant. Phenobarbital pretreatment lowered the extent of lipid peroxidation as measured by malonaldehyde production but had little effect on the rate of lipid peroxidation as measured by oxygen uptake. The kinetics of lipid peroxidation and the stoichiometry of the reaction were assessed as a function of dietary antioxidant.The findings suggest that at low microsomal antioxidant concentrations, the lipid peroxidation reaction occurs at a maximal rate dependent upon some rate-limiting step, such as the reduction of Fe+3, which is unaffected by CCl4 addition. Conversely, at high microsomal antioxidant concentrations, the antioxidant termination reactions appear to determine the overall reaction rate. 相似文献