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1.
Hirofumi Fukushima Shigenobu Umeki Takehito Watanabe Yoshinori Nozawa 《Biochemical and biophysical research communications》1982,105(2):502-508
With the use of detergents and successive column chromatographies, Tetrahymena b-type cytochrome was purified from microsomes to a specific content of 36.0 nmol per mg of protein. The purified form showed a single band on SDS-polyacrylamide gel with molecular weight of 22,000. The spectral properties of the reduced b-type cytochrome, the α-peak of which is situated at 560 nm and asymmetric with a shoulder at 556 nm, was different from that of rat liver microsomal cytochrome b5. However, it was reducible by NADH in the presence of NADH-cytochrome b5 reductase purified from rat liver microsomes.The results indicated that the microsomal b-type cytochrome should be designated as cytochrome b5 of a ciliated protozoan, Tetrahymena pyriformis. 相似文献
2.
Y Yoshida Y Aoyama H Kumaoka S Kubota 《Biochemical and biophysical research communications》1977,78(3):1005-1010
Cytochrome P-450 was purified from microsomes of anaerobically grown yeast to a specific content of 12–15 nmoles per mg of protein with a yield of 10–30%. Upon sodium dodecylsulfate/polyacrylamide gel electrophoresis, the purified preparation yielded a major protein band having a molecular weight of about 51,000 together with a few faint bands. It was free from cytochrome b5, NADH-cytochrome b5 reductase, and NADPH-cytochrome c (P-450) reductase. In the oxidized state it exhibited a low-spin type absorption spectrum, and its reduced CO complex showed a Soret peak at 447–448 nm. It was reducible by NADPH in the presence of an NADPH-cytochrome c reductase preparation purified from yeast microsomes. Its conversion to the cytochrome P-420 form was much slower than that of hepatic cytochrome P-450. 相似文献
3.
《Insect Biochemistry》1989,19(5):481-488
Cytochrome P-450, cytochrome b5 and cytochrome P-450 reductase were purified from house fly abdomens using high performance liquid chromatography (HPLC). Using a new technique, cytochrome P-450 was separated from the bulk of other proteins after polyethylene glycol fractionation and hydrophobic interaction chromatography (HIC) using a phenyl-5PW column. This technique resulted in 91% recovery of the cytochrome P-450s in a single concentrated fraction that also contained the remaining cytochrome b5 and cytochrome P-450 reductase activity. Further purification by anion exchange on a DEAE-5SW column resolved the cytochrome P-450s, cytochrome b5 and cytochrome P-450 reductase into individual fractions. The ion exchange step yielded one fraction that contained a high specific content of P-450 (14.4 nmol/mg protein). This cytochrome P-450 fraction ran as a single band at 54.3 kDa in sodium dodecyl sulfate polyacrylamide (SDS-PAGE) gel electrophoresis and had a carboxy ferrocytochrome absorbance maximum at 447 nm.Further purification of the anion exchange cytochrome b5 fraction, by C8 reverse phase HPLC, resulted in a cytochrome b5 fraction with a specific content of 51.8 nmol/mg protein and an apparent molecular mass of 19.7 kDa by SDS-PAGE. The anion exchange HPLC fraction containing the cytochrome P-450 reductase activity was further purified by NADP-agarose affinity chromatography. This step yielded cytochrome P-450 reductase with an apparent molecular mass of 72 kDa. 相似文献
4.
Shigetaka Kitajima Yukio Yasukochi Shigeki Minakami 《Archives of biochemistry and biophysics》1981,210(1):330-339
An NADH:(acceptor) oxidoreductase (EC 1.6.99.3) of human erythrocyte membrane was purified by DEAE-cellulose anion exchange, hydroxyapatite adsorption, and 5′-ADP-hexane-agarose affinity chromatographies after solubilization with Triton X-100. The purified reductase preparation was homogeneous and estimated to have an apparent molecular weight of 36,000 on SDS-polyacrylamide slab gel electrophoresis and of 144,000 on Sephadex G-200 gel filtration in the presence of 0.2% Triton X-100, whereas a soluble NADH-cytochrome b5 reductase of human erythrocyte had a molecular weight of 32,000 by both methods, indicating the existence of a distinct membrane reductase. Digestion of the membrane reductase with cathepsin D yielded a new polypeptide chain which gave the same relative mobility as the soluble reductase on SDS-polyacrylamide slab gel electrophoresis. The membrane enzyme, the cathepsin-digested enzyme, and the soluble enzyme all cross-reacted with the antibody to rat liver microsomal NADH-cytochrome b5 reductase. The enzyme had one mole FAD per 36,000 as a prosthetic group and could reduce K3Fe(CN)6, 2,6-dichlorophenolindophenol, cytochrome c, methemoglobin-ferrocyanide complex, cytochrome b5 and methemoglobin via cytochrome b5 when NADH was used as an electron donor. NADPH was less effective as an electron donor than NADH. The specific activity of the purified enzyme was 790 μmol ferricyanide reduced min?1 mg?1 and the turnover number was 40,600 mol ferricyanide reduced min?1 mol?1 FAD at 25 °C. The apparent Km values for NADH and cytochrome b5 were 0.6 and 20 μm, respectively, and the apparent V value was 270 μmol cytochrome b5 reduced min?1 mg?1. These kinetic properties were similar to those of the soluble NADH-cytochrome b5 reductase. The results indicate that the NADH:(acceptor) oxidoreductase of human erythrocyte membrane could be characterized as a membrane NADH-cytochrome b5 reductase. 相似文献
5.
《Journal of steroid biochemistry》1980,12(8):861-867
Addition of pregnenolone to guinea-pig adrenal microsomes produces a slowly developing difference spectrum with peaks at about 425 and 557 nm and a trough at about 410 nm. The spectral change is similar to that resulting from the reduction of cytochrome b5 by NADH or NADPH. In the presence of sufficient quantities of NADH to fully reduce cytochrome b5, pregnenolone produces a typical type I difference spectrum (ΔA385–420 nm). Pregnenolone is converted to progesterone by adrenal microsomes without addition of cofactor (NAD+) for the 3β-hydroxysteroid dehydrogenase (HSD) reaction. The rate of conversion is increased 2–3 fold by NAD+ and inhibited by NADH. Accompanying the metabolism of pregnenolone (with or without added NAD+) is the production of NADH and reduction of cytochrome b5. Addition of pregnenolone alone to adrenal microsomes results in 60–80% reduction of cytochrome b5. The reduction of cytochrome b5 is maintained for at least as long as pregnenolone is being metabolized. Inhibition of pregnenolone metabolism changes the pregnenolone-induced spectral change to a type I and prevents the reduction of cytochrome b5. The results suggest that the oxidation-reduction state of cytochrome b5 in adrenal microsomes is controlled in part by pregnenolone metabolism which in turn influences the pregnenolone-induced difference spectrum. Oxidation of NADH by cytochrome b5 may serve to prevent NADH inhibition of HSD activity and to generate additional NAD+ as cofactor for the reaction. 相似文献
6.
An antibody preparation elicited against purified, lysosomal-solubilized NADH-cytochrome b5 reductase from rat liver microsomes was shown to interact with methemoglobin reductase of human erythrocytes by inhibiting the rate of erythrocyte cytochrome b5 reduction by NADH. The ferricyanide reductase activity of the enzyme was not inhibited by the antibody, suggesting that the inhibition of methemoglobin reductase activity may be due to interference with the binding of cytochrorme b5 to the flavoprotein. Under conditions of limiting concentrations of flavoprotein, the antibody inhibited the rate of methemoglobin reduction in a reconstituted system consisting of homogeneous methemoglobin reductase and cytochrome b5 from human erythrocytes. This inhibition was due to the decreased level of reduced cytochrome b5 during the steady state of methemoglobin reduction while the rate of methemoglobin reduction per reduced cytochrome b5 stayed constant, suggesting that the enzyme was not concerned with an electron transport between the reduced cytochrome b5 and methemoglobin.An antibody to purified, trypsin-solubilized cytochrome b5 from rat liver microsomes was shown to inhibit erythrocyte cytochrome b5 reduction by methemoglobin reductase and NADH to a lesser extent than microsomal cytochrome b5 preparations from rat liver (trypsin solubilized or detergent solubilized) and pig liver (trypsin solubilized). The results presented establish that soluble methemoglobin reductase and cytochrome b5 of human erythrocytes are immunochemically similar to NADH-cytochrome b5 reductase and cytochrome b5 of liver microsomes, respectively. 相似文献
7.
The effects of culture variables on the specific content and activity of various enzymes of the drug mmetabolizing system were assessed in colon tumor cell line LS174T. The NADH reduced cytochrome b5 (cyt b5)4 spectrum of these cells was similar to rat liver cyt b5. When released from the membrane by trypsin and concentrated, the cyt b5 was found to cross react with rabbit antibody to rat liver cyt b5 and human liver cyt b5. The enzyme activities were found stable over limited cell passages with control values of 0.03 and 0.13 µol/min/mg protein for NADPH and NADH cytochrome c (cyt c) reducing activity, 0.05 nmol cyt b5 and 0.013 nmol cytochrome P450 per milligram of microsomal protein. Phenobarbital/hydrocortisone showed a consistent, but not always significant increase in the NADPH and NADH cyt c reduction and benzanthracene an increase in the NADH cyt c reducing activity and cyt b5 content. Griseofulvin lowered the NADH cyt c reducing activity. Delta-aminolevulinic acid (0.5 mM) caused a significant decrease in the specific activity of all enzymes, as judged by a student's t test, with a p<0.001.Abbreviations cyt b5
cytochrome b5
- cyt c
cytochrome c
- cyt P450
cytochrome P450
- PB
Phenobarbital
- HC
Hydrocortisone
- ALA
-Aminolevulinic acid
- GRIS
Griseofulvin
- PENT
Pentagastrin
- PASS
Cell Passage
- DMH
Dimethylhydrazine
- BA
Benzanth Acene 相似文献
8.
Bin Deng Sudharsan Parthasarathy WenFang Wang Brian R. Gibney Kevin P. Battaile Scott Lovell David R. Benson Hao Zhu 《The Journal of biological chemistry》2010,285(39):30181-30191
NADH cytochrome b5 oxidoreductase (Ncb5or) is found in animals and contains three domains similar to cytochrome b5 (b5), CHORD-SGT1 (CS), and cytochrome b5 reductase (b5R). Ncb5or has an important function, as suggested by the diabetes and lipoatrophy phenotypes in Ncb5or null mice. To elucidate the structural and functional properties of human Ncb5or, we generated its individual b5 and b5R domains (Ncb5or-b5 and Ncb5or-b5R, respectively) and compared them with human microsomal b5 (Cyb5A) and b5R (Cyb5R3). A 1.25 Å x-ray crystal structure of Ncb5or-b5 reveals nearly orthogonal planes of the imidazolyl rings of heme-ligating residues His89 and His112, consistent with a highly anisotropic low spin EPR spectrum. Ncb5or is the first member of the cytochrome b5 family shown to have such a heme environment. Like other b5 family members, Ncb5or-b5 has two helix-loop-helix motifs surrounding heme. However, Ncb5or-b5 differs from Cyb5A with respect to location of the second heme ligand (His112) and of polypeptide conformation in its vicinity. Electron transfer from Ncb5or-b5R to Ncb5or-b5 is much less efficient than from Cyb5R3 to Cyb5A, possibly as a consequence of weaker electrostatic interactions. The CS linkage probably obviates the need for strong interactions between b5 and b5R domains in Ncb5or. Studies with a construct combining the Ncb5or CS and b5R domains suggest that the CS domain facilitates docking of the b5 and b5R domains. Trp114 is an invariant surface residue in all known Ncb5or orthologs but appears not to contribute to electron transfer from the b5R domain to the b5 domain. 相似文献
9.
To understand the role of the structural elements of cytochrome b 5 in its interaction with cytochrome P450 and the catalysis performed by this heme protein, we carried out comparative structural and functional analysis of the two major mammalian forms of membrane-bound cytochrome b 5 — microsomal and mitochondrial, designed chimeric forms of the heme proteins in which the hydrophilic domain of one heme protein is replaced by the hydrophilic domain of another one, and investigated the effect of the highly purified native and chimeric heme proteins on the enzymatic activity of recombinant cytochromes P4503A4 and P45017A1 (CYP3A4 and CYP17A1). We show that the presence of a hydrophobic domain in the structure of cytochrome b 5 is necessary for its effective interaction with its redox partners, while the nature of the hydrophobic domain has no significant effect on the ability of cytochrome b 5 to stimulate the activity of cytochrome P450-catalyzed reactions. Thus, the functional properties of cytochrome b 5 are mainly determined by the structure of the hemebinding domain. 相似文献
10.
Hen liver microsomes contained 0.20 nmol of cytochromeb5 per mg of protein. Upon addition of NADH about 95% cytochrome b5 was reduced very fast with a rate constant of 206 s?1When ferricyanide was added to the reaction system the cytochrome stayed in the oxidized form until the ferricyanide reduction was almost completed. The reduced cytochrome b5 in microsomes was oxidized very rapidly by ferricyanide. The rate constant of 4.5 × 108m?1 s?1, calculated on the basis of assumption that ferricyanide reacts directly with the cytochrome, was found to be more than 100 times higher than that of the reaction between ferricyanide and soluble cytochrome b5. To explain the results, therefore, the reverse electron flow from cytochrome b5 to the flavin coenzyme in microsomes was assumed.By three independent methods the specific activity of the microsomes was measured at about 20 nmol of NADH oxidized per s per mg of protein and it was concluded that the reduction of the flavin coenzyme of cytochrome b5 reductase by NADH is rate-limiting in the NADH-cytochrome b5 and NADH-ferricyanide reductase reactions of hen liver microsomes. In the NADH-ferricyanide reductase reaction the apparent Michaelis constant for NADH was 2.8 μm and that for ferricyanide was too low to be measured. In the NADH-cytochrome c reductase reaction the maximum velocity was 2.86 nmol of cytochrome c reduced per s per mg of protein and the apparent Michaelis constant for cytochrome c was 3.8 μm. 相似文献
11.
Emma L. Reid Karen D. Weynberg John Love Michail N. Isupov Jennifer A. Littlechild William H. Wilson Steven L. Kelly David C. Lamb Michael J. Allen 《FEBS letters》2013
Cytochrome b5 is a ubiquitous electron transport protein. The sequenced viral OtV-2 genome, which infects Ostreococcus tauri, was predicted to encode a putative cytochrome b5 enzyme. Using purified OtV-2 cytochrome b5 we confirm this protein has identical spectral properties to purified human cytochrome b5 and additionally that the viral enzyme can substitute for yeast cytochrome b5 in yeast cytochrome P450 51 mediated sterol 14α-demethylation. The crystal structure of the OtV-2 cytochrome b5 enzyme reveals a single domain, comprising four β sheets, four α helices and a haem moiety, which is similar to that found in larger eukaryotic cytochrome proteins. As a product of a horizontal gene transfer event involving a subdomain of the host fumarate reductase-like protein, OtV-2 cytochrome b5 appears to have diverged in function and is likely to have evolved an entirely new role for the virus during infection. Indeed, lacking a hydrophobic C-terminal anchor, OtV-2 encodes the first cytosolic cytochrome b5 characterised. The lack of requirement for membrane attachment (in contrast to all other microsomal cytochrome b5s) may be a reflection of the small size of the host cell, further emphasizes the unique nature of this virus gene product and draws attention to the potential importance of cytochrome b5 metabolic activity at the extremes of cellular scale. 相似文献
12.
The Structure of Calf Liver Cytochrome <Emphasis Type="Italic">b</Emphasis><Subscript>5</Subscript> at 2.8 Å Resolution 总被引:5,自引:0,他引:5
CYTOCHROME b5 is a haem-containing protein in the microsomes of liver tissue. It interacts specifically with a flavo-protein, cytochrome b5 reductase, which catalyses the transfer of electrons from NADH to the haem iron of the cytochrome1. The microsomal cytochrome b5 system has been implicated in fatty acid desaturation reactions2 and a similar system in erythrocytes may catalyse the reduction of methaemoglobin3. Calf liver cytochrome b5, solubilized by pancreatic lipase, has a molecular weight of 11,000 and consists of ninety-three amino-acids in the sequence shown in Fig. 1 (refs. 4 and 5). The haem group is non-covalently bound to the protein and can be removed reversibly by acid acetone treatment6. 相似文献
13.
(i) Compounds activating the microsomal electron transfer oxidative reactions, e.g., the mixed function oxidase (aminopyrine, aniline), the Δ9-desaturase (stearyl-CoA), and lipid peroxidation reaction (iron pyrophosphate), cause a decrease in the steady-state reduced level of cytochrome b5. (ii) In the absence of substrates, the kox for cytochrome b5 was the same whether reduced by NADH or NADPH (about 0.045 S?1, indicating that no distinction exists between the cytochrome b5 involved in NADH-driven and NADPH-driven microsomal reactions which utilize this hemoprotein. (iii) The agents activating the oxidative pathways affect the first-order rate constant for cytochrome b5 oxidation (kox), but the apparent first-order rate constant obtained for reduction (kred) of cytochrome b5 by NADPH is still more than 10 times the kox, and the kred obtained with NADH is still more than 100 times the kox. (iv) Of the compounds used, only stearyl-CoA caused a decrease in the NADH-supported steady-state reduced level of cytochrome b5. This effect is probably due to a detergent-like action of stearyl-CoA on the membrane proteins, interfering with some interactions (e.g., NADPH-cytochrome c reductase with cytochrome P-450; NADH-cytochrome b5 reductase with cytochrome b5). (v) Based upon the kinetic and steady-state measurements it is concluded that substrate-induced changes in the steady-state reduced level of cytochrome b5 are evidence for a decrease in the population of this hemoprotein available to the reductase due to competition with other more favored acceptors, (vi) Measurements using the duration of the reduced state and rates of electron flow through cytochrome b5 reveal that normally about 60% of the NADH-derived reducing equivalents go through cytochrome b5 while only about one electron in nine passes through this cytochrome when NADPH is the source of reducing equivalents. Substrates of the various pathways alter the proportion of electrons passing through cytochrome b5 depending upon their activating or inhibiting action on cytochrome b5-dependent or -independent reactions. 相似文献
14.
Cytochrome b5 purified from neonatal pig testis and that from pig liver stimulated C21 steroid side-chain cleavage (progesterone → androstenedione) catalyzed in vitro by purified cytochrome P-450 from neonatal pig testicular microsomes. Km of testicular cytochrome b5 for the P-450 is 6.3–9.1 × 10?8M and the ability of b5 to stimulate C21 side-chain cleavage is different for cytochromes b5 prepared from different sources. 相似文献
15.
Incubation in the presence of NADPH and molecular oxygen of 14C-labeled polychlorinated biphenyls (PCBs) and two tetrachlorobiphenyl (TCB) isomers with a reconstituted system containing NADPH-cytochrome P-450 reductase and cytochrome P-450, both purified from liver microsomes of phenobarbital(PB)-pretreated rabbits, led to covalent binding of radioactive metabolites of PCBs and TCBs to the protein components of the system. A rabbit liver cytosol fraction added to the system provided more binding sites for the activated metabolites and thus increased the extent of binding markedly. The binding reaction depended absolutely on the reductase, cytochrome P-450 and NADPH, and required dilauroyl phosphatidylcholine and sodium cholate for maximal activity. A further stimulation of the binding was attained by including cytochrome b5 in the reconstituted system. Four forms of cytochrome P-450, purified from liver microsomes of PB- and 3-methylcholanthrene(MC)-treated rabbits and rats, were used to reconstitute the PCB- and TCB-metabolizing systems, and it was found that PB-inducible forms of the cytochrome from both animals were more active than those inducible by MC in catalyzing the PCB- and TCB-binding reaction. Sodium dodecyl sulfate(SDS)-polyacrylamide gel electrophoresis indicated that, in the system containing the reductase, cytochrome P-450 and cytochrome b5, PCB metabolites bound to the reductase and cytochrome P-450, but not to cytochrome b5. In the presence of the liver cytosol fraction, the binding took place to many cytosolic proteins in addition to the reductase and cytochrome P-450. 相似文献
16.
A I Archakov V M Devichensky A V Karjakin 《Archives of biochemistry and biophysics》1975,166(1):295-307
The rate of the redox reactions of cytochromes b5 and P-450 in the presence of NADPH and NADH has been studied. It has been shown that different factors: dimethylaniline, ferric pyrophosphate, carbon monoxide, and an increase in the ionic strength of the medium produce a similar effect on the rate of the redox reactions of cytochromes b5 and P-450 reduced by NADPH. With NADH used as substrate, aerobic redox behavior of cytochrome b5 was quite different. The data obtained gave grounds to suggest a scheme of electron transfer in the NADPH oxidation chain according to which one of the cytochrome b5 subfractions (about 25% of the total pool of cytochrome b5) functions between flavoprotein and cytochrome P-450. 相似文献
17.
A cytochrome b-c1 complex was isolated from pigeon breast muscle mitochondria and purified to a content of 3 nmol of cytochrome c1 per milligram of protein. Anaerobic suspensions of the preparation were titrated with reducing equivalents (NADH) and oxidizing equivalents (ferricyanide). The oxidation-reduction components of the complex were measured by the number of reducing equivalents accepted or donated per cytochrome c1 and compared with the stoichiometries of the known redox components as measured by independent methods. The preparation accepts or donates 5.2 ± 0.3 equivalents per cytochrome c1, while the measured content of cytochrome c1, cytochrome b561, cytochrome b565, Rieske iron-sulfur protein, ubiquinone, and succinate dehydrogenase accounts for 5.0 ± 0.2 equivalents per cytochrome c1. It is concluded that there are no unknown redox components in the cytochrome b-c1 complex. The cytochrome b-c1 complex (energy transduction site 2) appears to be a structural unit containing equal amounts of cytochrome c1, cytochrome b561, cytochrome b566, and the Rieske iron-sulfur protein. 相似文献
18.
The incorporation of radioactive amino acids and of δ-amino[2,3-3H2]laevulinate into rat liver cytochromes b5 and c and cytochrome oxidase has been examined with and without protein-synthesis inhibitors. Cycloheximide promptly inhibits labelling of both haem and protein for cytochrome c in parallel fashion. Although incorporation of 14C-labelled amino acid into microsomal cytochrome b5 is also rapidly inhibited, cycloheximide incompletely inhibits haem labelling of cytochrome b5 and cytochrome a+a3, and inhibition occurs only after repeated antibiotic injections. The possibility of apo-protein pools, or of haem exchange, with a rapidly renewed `free' haem pool, is considered. Consistent with this model is the observation of non-enzymic haem exchange in vitro between cytochrome b5 and methaemoglobin. Chloramphenicol, injected intravenously over 5h, results in a 20–40% decrease in incorporation of δ-amino[2,3-3H2]laevulinate into haem a+a3 and haem of cytochromes b5 and c. With the dosage schedule of chloramphenicol studied, amino acid labelling of total liver protein and of cytochrome c was not inhibited. Similarly, ferrochelatase activity was not decreased. 相似文献
19.
Masayuki Katagiri Katsuko Suhara Masahiro Shiroo Yoshiyuki Fujimura 《Biochemical and biophysical research communications》1982,108(1):379-384
The cytochrome P-450 (P-450sccII) and its reductase, NADPH-cytochrome reductase [EC 1.6.2.4], associated with conversion of progesterone to 4-androstene-3,17-dione, were extensively purified from pig testis microsomes. Higher lyase activity (turnover number of 15 mol of the product formed/min/mol of P-450) could be restored by mixing the P-450sccII, its reductase, pig liver cytochrome b5 and cytochrome b5-reductase [EC 1.6.2.2], and phospholipid in the presence of NADPH, NADH, and O2. Omission of either cytochrome b5 or NADH resulted in a significant loss of the lyase activity indicating actual participation of cytochrome b5 in this P-450-mediated steroidogenic system in the testis. 相似文献
20.
Purification and Characterization of Microsomal Cytochrome b(5) and NADH Cytochrome b(5) Reductase from Pisum sativum 总被引:2,自引:2,他引:0
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In this communication we document the reproducible protocols for the purification of milligram quantities of cytochrome b5 and NADH-cytochrome b5 reductase from the microsomal fraction of Pisum sativum. The cytochrome b5 component of this NADH linked electron transport chain was found to have a molecular mass of 16,400 daltons and the reductase a molecular mass of 34,500 daltons. These components could be reconstituted into a functional NADH oxidase activity active in the reduction of exogenous cytochrome c or ferricyanide. In the latter assay the purified reductase exhibited a turnover number of 22,000 per minute. The amino-terminal amino acid sequence of the cytochrome b5 component was determined by sequential Edmund degredation, thus providing crucial information for the efficient cloning of this central protein of plant microsomal electron transfer. 相似文献