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Rhieu SY, Annalora AJ, LaPorta E, Welsh J, Itoh T, Yamamoto K, Sakaki T, Chen TC, Uskokovic MR, Reddy GS. Potent antiproliferative effects of 25-hydroxy-16-ene-23-yne-vitamin D₃ that resists the catalytic activity of both CYP27B1 and CYP24A1. J Cell Biochem 2015; 115:1392-402. [PMID: 24535953 DOI: 10.1002/jcb.24789] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 02/14/2014] [Indexed: 11/06/2022]
Abstract
The potency of 25-hydroxyvitamin D3 (25(OH)D3) is increased by several fold through its metabolism into 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) by cytochrome P450 27B1 (CYP27B1). Thus, the pivotal role of 1α-hydroxylation in the activation of vitamin D compounds is well known. Here, we examined the metabolism of 25-hydroxy-16-ene-23-yne-vitamin D3 (25(OH)-16-ene-23-yne-D3), a synthetic analog of 25(OH)D3 in a cell-free system and demonstrated that 25(OH)-16-ene-23-yne-D3 is neither activated by CYP27B1 nor inactivated by cytochrome P450 24A1 (CYP24A1). These findings were also confirmed in immortalized normal human prostate epithelial cells (PZ-HPV-7) which are known to express both CYP27B1 and CYP24A1, indicating that the structural modifications featured in 25(OH)-16-ene-23-yne-D3 enable the analog to resist the actions of both CYP27B1 and CYP24A1. To provide intelligible structure-function information, we also performed molecular docking analysis between the analog and CYP27B1. Furthermore, 25(OH)-16-ene-23-yne-D3 was found to suppress the growth of PZ-HPV-7 cells with a potency equivalent to 1α,25(OH)2D3. The antiproliferative activity of 25(OH)-16-ene-23-yne-D3 was found to be vitamin D receptor (VDR)-dependent as it failed to inhibit the growth of mammary tumor cells derived from VDR-knockout mice. Furthermore, stable introduction of VDR into VDR-knockout cells restored the growth inhibition by 25(OH)-16-ene-23-yne-D3. Thus, we identified 25-hydroxy-16-ene-23-yne-vitamin D3 as a novel non-1α-hydroxylated vitamin D analog which is equipotent to 1α,25(OH)2D3 in its antiproliferative activity. We now propose that the low potency of the intrinsic VDR-mediated activities of 25(OH)D3 can be augmented to the level of 1α,25(OH)2D3 without its activation through 1α-hydroxylation by CYP27B1, but by simply preventing its inactivation by CYP24A1.
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Affiliation(s)
- Steve Y Rhieu
- Epimer LLC, North Smithfield, Rhode Island, 02896, USA
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2
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Rhieu SY, Annalora AJ, Wang G, Flarakos CC, Gathungu RM, Vouros P, Sigüeiro R, Mouriño A, Schuster I, Palmore GTR, Reddy GS. Metabolic stability of 3-Epi-1α,25-dihydroxyvitamin D3over 1α, 25-dihydroxyvitamin D3: Metabolism and molecular docking studies using rat CYP24A1. J Cell Biochem 2013; 114:2293-305. [DOI: 10.1002/jcb.24576] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 04/12/2013] [Indexed: 11/08/2022]
Affiliation(s)
| | - Andrew J. Annalora
- Department of Molecular Biology; The Scripps Research Institute; La Jolla; California; 92037
| | | | - Caroline C. Flarakos
- Department of Chemistry and Chemical Biology; Northeastern University; Boston; Massachusetts; 02115
| | - Rose M. Gathungu
- Department of Chemistry and Chemical Biology; Northeastern University; Boston; Massachusetts; 02115
| | - Paul Vouros
- Department of Chemistry and Chemical Biology; Northeastern University; Boston; Massachusetts; 02115
| | - Rita Sigüeiro
- Departamento de Química Orgánica, Laboratorio de Investigación Ignacio Ribas; Universidad de Santiago de Compostela; E-15706; Santiago de Compostela; Spain
| | - Antonio Mouriño
- Departamento de Química Orgánica, Laboratorio de Investigación Ignacio Ribas; Universidad de Santiago de Compostela; E-15706; Santiago de Compostela; Spain
| | - Inge Schuster
- Institute for Theoretical Chemistry; University of Vienna; Vienna; Austria
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3
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Rhieu SY, Annalora AJ, Gathungu RM, Vouros P, Uskokovic MR, Schuster I, Palmore GTR, Reddy GS. A new insight into the role of rat cytochrome P450 24A1 in metabolism of selective analogs of 1α,25-dihydroxyvitamin D₃. Arch Biochem Biophys 2011; 509:33-43. [PMID: 21338573 DOI: 10.1016/j.abb.2011.02.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2010] [Revised: 02/03/2011] [Accepted: 02/08/2011] [Indexed: 10/18/2022]
Abstract
We examined the metabolism of two synthetic analogs of 1α,25-dihydroxyvitamin D₃ (1), namely 1α,25-dihydroxy-16-ene-23-yne-vitamin D₃ (2) and 1α,25-dihydroxy-16-ene-23-yne-26,27-dimethyl-vitamin D₃ (4) using rat cytochrome P450 24A1 (CYP24A1) in a reconstituted system. We noted that 2 is metabolized into a single metabolite identified as C26-hydroxy-2 while 4 is metabolized into two metabolites, identified as C26-hydroxy-4 and C26a-hydroxy-4. The structural modification of adding methyl groups to the side chain of 1 as in 4 is also featured in another analog, 1α,25-dihydroxy-22,24-diene-24,26,27-trihomo-vitamin D₃ (6). In a previous study, 6 was shown to be metabolized exactly like 4, however, the enzyme responsible for its metabolism was found to be not CYP24A1. To gain a better insight into the structural determinants for substrate recognition of different analogs, we performed an in silico docking analysis using the crystal structure of rat CYP24A1 that had been solved for the substrate-free open form. Whereas analogs 2 and 4 docked similar to 1, 6 showed altered interactions for both the A-ring and side chain, despite prototypical recognition of the CD-ring. These findings hint that CYP24A1 metabolizes selectively different analogs of 1, based on their ability to generate discrete recognition cues required to close the enzyme and trigger the catalytic mechanism.
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Zhu J, Barycki R, Chiellini G, Deluca HF. Screening of selective inhibitors of 1α,25-dihydroxyvitamin D3 24-hydroxylase using recombinant human enzyme expressed in Escherichia coli. Biochemistry 2010; 49:10403-11. [PMID: 21058632 DOI: 10.1021/bi101488p] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
High-level heterologous expression of human 1α,25-dihydroxyvitamin D(3) 24-hydroxylase (CYP24A1) in Escherichia coli was attained via a fusion construct by appending the mature CYP24A1 without the leader sequence to the maltose binding protein (MBP). Facile purification was achieved efficiently through affinity chromatography and afforded fully functional enzyme of near homogeneity, with a k(cat) of 0.12 min(-1) and a K(M) of 0.19 μM toward 1α,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. A convenient and reliable cell-free assay was established and used to screen vitamin D analogues with potential inhibitory properties toward CYP24A1. Some of the compounds exhibited potent inhibition with K(I) values as low as 0.021 μM. Furthermore, TS17 and CPA1 exhibited superior specificity toward CYP24A1 over 25-hydroxyvitamin D(3) 1α-hydroxylase (CYP27B1), with selectivities of 39 and 80, respectively. Addition of TS17 or CPA1 to a mouse osteoblast culture sustained the level of 1,25(OH)(2)D(3) in the medium. Their activities in vitamin D receptor (VDR) binding, CYP24A1 transcription, and HL-60 cell differentiation were evaluated as well.
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Affiliation(s)
- Jinge Zhu
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, Wisconsin 53706, United States
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5
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Strushkevich NV, Harnastai IN, Usanov SA. Mechanism of steroidogenic electron transport: role of conserved Glu429 in destabilization of CYP11A1-adrenodoxin complex. BIOCHEMISTRY (MOSCOW) 2010; 75:570-8. [PMID: 20632935 DOI: 10.1134/s0006297910050056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In the present work the role of conserved residue E429 of cytochrome P45011A1 has been studied. The charge neutralization of E429Q results in 3-fold decrease of K(d) as well as V(max) compared to the wild type hemoprotein indicating tighter binding and, as the result, the impaired dissociation of oxidized adrenodoxin from the complex. As cytochrome P45011A1-adrenodoxin complex formation is driven primarily by electrostatic interactions, the low activity of E429Q mutant is completely restored to that of wild type hemoprotein by increasing of ionic strength. The charge neutralization of the corresponding residue of rat cytochrome P45011B2 has the same effect: the activity is 10-fold decreased but it is restored by increasing of ionic strength without effect on the ratio of products formed. Thus, this is the first report on identification of residues involved in modulation of dissociation of redox partner from the complex with cytochrome P450s.
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Affiliation(s)
- N V Strushkevich
- Institute of Bioorganic Chemistry, Academy of Sciences of Belarus, Minsk, 220141, Belarus
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6
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Annalora A, Bobrovnikova-Marjon E, Serda R, Lansing L, Chiu ML, Pastuszyn A, Iyer S, Marcus CB, Omdahl JL. Rat cytochrome P450C24 (CYP24A1) and the role of F249 in substrate binding and catalytic activity. Arch Biochem Biophys 2004; 425:133-46. [PMID: 15111121 DOI: 10.1016/j.abb.2004.01.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Revised: 01/17/2004] [Indexed: 10/26/2022]
Abstract
A high level of functional recombinant rat cytochrome P450C24 enzyme (CYP24A1) was obtained (40-50mg/L) using an Escherichia coli expression system. Purified enzyme was stable with retention of spectral and catalytic activity. The rate of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] side-chain oxidation and cleavage to the end-product calcitroic acid was directly related to the rate of electron transfer from the ferredoxin redox partner. It was determined from substrate-induced spectral shifts that the 1 alpha- and 25-hydroxyl groups on vitamin D(3) metabolites and analogs were the major determinants for high-affinity binding to CYP24A1. Lowest K(d) values were obtained for 1 alpha-vitamin D(3) (0.06 microM) and 1,25-dihydroxyvitamin D(3) (0.05 microM) whereas unmodified parental vitamin D(3) and the non-secosteroid 25-hydroxycholesterol had lower affinities with K(d) values of 1.3 and 1.9 microM, respectively. The lowest binding affinity for natural vitamin D metabolites was observed for 24,25-dihydroxyvitamin D(3) [24,25(OH)(2)D(3)] (0.43 microM). Kinetic analyses of the two natural substrates 25-hydroxyvitamin D(3) [25(OH)D(3)] and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] revealed similar K(m) values (0.35 and 0.38 microM, respectively), however, the turnover number was higher for 25(OH)D(3) compared to 1,25(OH)(2)D(3) (4.2 and 1 min(-1), respectively). Mutagenesis of F249 within the F-helix of CYP24A1 altered substrate binding and metabolism. Most notable, the hydrophobic to polar mutant F249T had a strong impact on lowering substrate-binding affinity and catalysis of the final C(23) oxidation sequence from 24,25,26,27-tetranor-1,23-dihydroxyvitamin D(3) to calcitroic acid. Two other hydrophobic 249 mutants (F249A and F249Y) also lowered substrate binding and expressed metabolic abnormalities that included the C(23)-oxidation defect observed with mutant F249T plus a similar defect involving an earlier pathway action for the C(24) oxidation of 1,24,25-trihydroxyvitamin D(3). Therefore, Phe-249 within the F-helix was demonstrated to have an important role in properly binding and aligning substrate in the CYP24A1 active site for C(23) and C(24) oxidation reactions.
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Affiliation(s)
- Andrew Annalora
- Department of Biochemistry and Molecular Biology, University of New Mexico School of Medicine, Albuquerque, NM 87131-5221, USA
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7
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Schiffler B, Zöllner A, Bernhardt R. Stripping down the mitochondrial cholesterol hydroxylase system, a kinetics study. J Biol Chem 2004; 279:34269-76. [PMID: 15181009 DOI: 10.1074/jbc.m402798200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The origin of steroid hormones in mammals is cholesterol that is metabolized by the mitochondrial CYP11A1 system. The cytochrome P450 is fed with reduction equivalents via a small electron transfer chain consisting of NADPH, adrenodoxin reductase, and adrenodoxin. Though the redox behavior of the individual protein components has been studied previously, the kinetics of the system in its entirety has not yet been analyzed. In this study we combine surface plasmon resonance experiments to determine the binding constants for the different pairs of redox partners with measurements of the pre-steady-state kinetics of the different reaction steps of this system and steady-state kinetics. We could correlate the individual protein-protein interactions with the effect of distinct reduction-oxidation steps on the overall catalytic activity of the CYP11A1 system. For the first time, we were able to follow the reduction of each of the protein components of this system within one measurement when we mixed all oxidized protein components with NADPH. These measurements allowed the determination of the individual apparent rate constants for the reduction of all three proteins involved. In addition, variation of the ionic strength in these experiments revealed different optimum salt concentrations for the reduction of adrenodoxin reductase and adrenodoxin, respectively, and unraveled dramatically changing reduction rates of CYP11A1 by adrenodoxin.
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Affiliation(s)
- Burkhard Schiffler
- Naturwissenschaftlich-Technische Fakultät III, FR 8.8-Biochemie, Universität des Saarlandes, P. O. Box 151150, D-66041 Saarbrücken, Germany
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8
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Abstract
A major biologic role of the ubiquitous mitochondrial P450 enzyme CYP27A1 is the generation of ligands such as 27-hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid, which regulate the expression of nuclear receptors that govern many aspects of cholesterol homeostasis. We now report that sterol intermediates in cholesterol synthesis, beginning with the initial post-cyclization sterol, lanosterol, continuing with zymosterol, and ending with desmosterol are also substrates for the enzyme. Using the human enzyme expressed in Escherichia coli, we characterized the retention times and major mass fragments of these novel metabolites. Although sequestration of the enzyme in the inner mitochondrial membrane and normal subcellular organization probably greatly restrict the proportion of these and other intermediates in cholesterol synthesis that undergo side chain oxidation, disruption of compartmentalization can bypass cholesterol as the end product and give rise to potent ligands that further modify gene expression.
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Affiliation(s)
- Irina Pikuleva
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-103, USA.
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9
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Ohno S, Shinoda S, Toyoshima S, Nakazawa H, Makino T, Nakajin S. Effects of flavonoid phytochemicals on cortisol production and on activities of steroidogenic enzymes in human adrenocortical H295R cells. J Steroid Biochem Mol Biol 2002; 80:355-63. [PMID: 11948020 DOI: 10.1016/s0960-0760(02)00021-3] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inhibitory effects of flavonoid phytochemicals, flavones, flavonols and isoflavones on cortisol production were examined in human adrenal H295R cells stimulated with di-buthylyl cAMP. In addition, the inhibitory effects of these chemicals on the activity of P450scc, 3beta-HSD type II (3beta-HSD II), P450c17, P450c21 and P45011beta, steroidogenic enzymes involved in cortisol biosynthesis, were examined in the same cells. Exposure to 12.5 microM of the flavonoids 6-hydroxyflavone, 4'-hydroxyflavone, apigenin, daidzein, genistein and formononetin significantly decreased cortisol production (by 6.3, 69.6, 47.5, 26.6, 13.8 and 11.3%, respectively), and biochanin A significantly decreased cortisol production (by 47.3%) at a concentration of 25 microM without any significant cytotoxic effects or changes in cell number. Daidzin, the 7-glucoside of daidzein, did not alter cortisol production by H295R cells at concentrations over 10 microg/ml (24 microM). Daidzein-induced reduction of cortisol production by H295R cells was not inhibited by the estrogen receptor antagonist ICI 182,780. The flavonoids 6-hydroxyflavone, daidzein, genistein, biochanin A and formononetin strongly and significantly inhibited microsomal 3beta-HSD II activity at concentrations from 1 to 25 microM, and I(50) values were estimated to be 1.3, 2, 1, 0.5 and 2.7 microM, respectively. In addition, these flavonoids significantly inhibited microsomal P450c21 activity at 12.5 and/or 25 microM. In addition, 6-hydroxyflavone inhibited activity of microsomal P450c17 and mitochondrial P45011beta at 12.5 and/or 25 microM. Results of Lineweaver-Burk's plot analysis indicate that daidzein is a competitive inhibitor of the activity of 3beta-HSD II and P450c21. K(m) and V(max) values of 3beta-HSD II for DHEA were estimated to be 6.6 microM and 328pmol/minmg protein, respectively. K(m) and V(max) values of P450c21 for progesterone were estimated to be 2.8 microM and 16pmol/minmg protein, respectively. K(i) values of 3beta-HSD II and P450c21 for daidzein were estimated to be 2.9 and 33.3 microM, respectively.
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Affiliation(s)
- Shuji Ohno
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
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10
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Hara T, Koba C, Takeshima M, Sagara Y. Evidence for the cluster model of mitochondrial steroid hydroxylase system derived from dissociation constants of the complex between adrenodoxin reductase and adrenodoxin. Biochem Biophys Res Commun 2000; 276:210-5. [PMID: 11006108 DOI: 10.1006/bbrc.2000.3462] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using biotinylated adrenodoxin and avidin-Sepharose 4B, dissociation constants for the complex between adrenodoxin reductase and adrenodoxin in the oxidized and reduced states were determined as 50 +/- 11 and 296 +/- 44 nM, respectively. Concentrations of adrenodoxin reductase/adrenodoxin in the matrix fraction from bovine adrenal cortex, liver, and kidney mitochondria were determined to be 20.2 +/- 10.6 microM/120 +/- 23 microM, 0.17 +/- 0.06 microM/1.79 +/- 0.24 microM, and 0.40 +/- 0.23 microM/1.33 +/- 0.26 microM, respectively. The calculation of the percentage of adrenodoxin reductase in the complex form in the reduced state showed that it is higher than 99% in adrenal cortex mitochondria, providing clear evidence for the cluster model for the mitochondrial steroid hydroxylase system.
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Affiliation(s)
- T Hara
- Department of Biochemistry, Graduate School of Health and Nutrition Sciences, Nakamura Gakuen University, 5-7-1 Befu, Jonan-ku, Fukuoka, 814-0198, Japan.
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11
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Pikuleva IA, Babiker A, Waterman MR, Björkhem I. Activities of recombinant human cytochrome P450c27 (CYP27) which produce intermediates of alternative bile acid biosynthetic pathways. J Biol Chem 1998; 273:18153-60. [PMID: 9660774 DOI: 10.1074/jbc.273.29.18153] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The primary physiological significance of cytochrome P450c27 (CYP27) has been associated with its role in the degradation of the side chain of C27 steroids in the hepatic bile acid biosynthesis pathway, which begins with 7alpha-hydroxylation of cholesterol in liver. However, recognition that in humans P450c27 is a widely or ubiquitously expressed mitochondrial P450, and that there are alternative pathways of bile acid synthesis which begin with 27-hydroxylation of cholesterol catalyzed by P450c27, suggests the need to reevaluate the role of this enzyme and its catalytic properties. 27-Hydroxycholesterol was thought to be the only product formed upon reaction of P450c27 with cholesterol. However, the present study demonstrates that recombinant human P450c27 is also able to further oxidize 27-hydroxycholesterol giving first an aldehyde and then 3beta-hydroxy-5-cholestenoic acid. Kinetic data indicate that in a reconstituted system, after 27-hydroxycholesterol is formed from cholesterol, it is released from the P450 and then competes with cholesterol for reentry the enzyme active site for further oxidation. Under subsaturating substrate concentrations, the efficiencies of oxidation of 27-hydroxycholesterol and 3beta-hydroxy-5-cholestenal to the acid by human P450c27 are greater than the efficiency of hydroxylation of cholesterol to 27-hydroxycholesterol indicating that the first hydroxylation step in the overall conversion of cholesterol into 3beta-hydroxy-5-cholestenoic acid is rate-limiting. Interestingly, 3beta-hydroxy-5-cholestenoic acid was found to be further metabolized by the recombinant human P450c27, giving two monohydroxylated products with the hydroxyl group introduced at different positions on the steroid nucleus.
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Affiliation(s)
- I A Pikuleva
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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12
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Lehnerer M, Schulze J, Petzold A, Bernhardt R, Hlavica P. Rabbit liver cytochrome P-450 2B5: high-level expression of the full-length protein in Escherichia coli, purification, and catalytic activity. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1245:107-15. [PMID: 7654758 DOI: 10.1016/0304-4165(95)00075-m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Rabbit liver cytochrome P-450 2B5 (P-450 2B5) was expressed in Escherichia coli using the D(+)-galactose-inducible expression vector pJL-2, containing the full-length cDNA encoding P-450 2B5. Stimulation by galactose of protein synthesis in the presence of the heme precursor 5-aminolevulinic acid peaked 72 h after addition to the inducer to yield 108 nmol membrane-bound P-450 2B5 per liter of culture medium. The recombinant enzyme was purified to near homogeneity by a two-column procedure involving chromatography on DE-52 cellulose and hydroxylapatite. The hemoprotein was isolated mainly in the low-spin iron configuration and exhibited a reduced CO-difference spectrum with a Soret band at 451 nm. Second-derivative spectral analysis in the middle-UV region revealed that type I binding of 4-nitroanisole to ferric P-450 2B5 abolished absorption bands ascribable to tyrosine residues within the polypeptide chain. Pseudo-first-order rates of NADPH-driven reduction of the pigment were lower when reconstituted with NADPH-cytochrome P-450 reductase than with the mitochondrial adrenodoxin/NADPH-adrenodoxin reductase redox couple. The enzyme was catalytically active toward 4-nitroanisole and androstenedione; metabolic rates were enhanced to different extents by the presence of cytochrome b5. The recombinant hemoprotein did not catalyze bioactivation of 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone, a potent pulmonary carcinogen. The methods described here should facilitate further studies on the biophysical basis of the complex interactions of P-450 2B5 with its redox partners.
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Affiliation(s)
- M Lehnerer
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Universität München, Germany
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13
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Shergill JK, Cammack R, Chen JH, Fisher MJ, Madden S, Rees HH. EPR spectroscopic characterization of the iron-sulphur proteins and cytochrome P-450 in mitochondria from the insect Spodoptera littoralis (cotton leafworm). Biochem J 1995; 307 ( Pt 3):719-28. [PMID: 7741702 PMCID: PMC1136710 DOI: 10.1042/bj3070719] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
EPR spectroscopy was used to investigate the cytochrome P-450-dependent steroid hydroxylase ecdysone 20-mono-oxygenase of the cotton leafworm (Spodoptera littoralis) and the redox centres associated with membranes from the fat-body mitochondrial fraction. Intense features at g = 2.42, 2.25 and 1.92 from oxidized mitochondrial membranes have been assigned to the low-spin haem form of ferricytochrome P-450, probably of ecdysone 20-mono-oxygenase. High-spin cytochrome P-450 (substrate-bound) was tentatively assigned to a signal at g = 8.0, which was detectable from membranes as prepared. An EPR signal characteristic of a [2Fe-2S] cluster detected from the soluble mitochondrial matrix fraction has been shown to be distinct from the signals associated with mitochondrial NADH dehydrogenase and succinate dehydrogenase, and has therefore been attributed to a ferredoxin. We conclude that the S. littoralis fat-body mitochondrial electron-transport system involved in steroid 20-hydroxylation comprises both ferredoxin and cytochrome P-450 components, and thus resembles the enzyme systems of adrenocortical mitochondria. EPR signals characteristic of the respiratory chain were also observed from fat-body mitochondria and assigned to the iron-sulphur clusters associated with Complex I (Centres N1, N2), Complex II (Centres S1, S3), Complex III (the Rieske centre), and the copper centre of Complex IV, demonstrating similarities to mammalian mitochondria. The reduced membrane fraction also yielded a major resonance at g = 2.09 and 1.88 characteristic of the [4Fe-4S] cluster of electron-transferring flavoprotein: ubiquinone oxidoreductase. As the fat-body is the major metabolic organ of insects, this protein is presumably required for the beta-oxidation of fatty acids in mitochondria. High-spin haem signals in the low-field region of spectra also demonstrated that the mitochondrial fraction contains relatively high concentrations of catalase.
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Affiliation(s)
- J K Shergill
- Centre for the Study of Metals in Biology and Medicine, King's College, University of London, U.K
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14
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Sagara Y, Matsunaga K, Nakamura K, Aramaki H, Watanabe Y, Hara T, Sekimizu K, Horiuchi T. Purification and characterization of rat adrenodoxin. Biochimie 1995; 77:719-23. [PMID: 8789462 DOI: 10.1016/0300-9084(96)88188-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Adrenodoxin was purified from the rat adrenal gland. The A414/A280 value of the purified rat adrenodoxin was 0.90 and the oxidized spectrum showed absorption maxima at 320, 414 and 455 nm, similar to those of bovine adrenodoxin. On SDS-PAGE, the rat adrenodoxin showed a single band with a molecular mass of 11.2 kDa, while the apparent molecular mass by gel filtration through Sephadex G-75 equilibrated with 10 mM K-phosphate (pH 7.5) was 27 kDa. In the reconstituted system, Vmax of NADPH-cytochrome c reduction activity and the Km for the rat adrenodoxin were much the same as those for recombinant bovine adrenodoxin. In the case of cholesterol side-chain cleavage activity, however, these values of the rat adrenodoxin were about half of those of the bovine adrenodoxin. The CD spectrum of the rat adrenodoxin was similar to that of the bovine adrenodoxin but showed a significantly lower ellipticity value in the 195-205 nm region than that of the bovine adrenodoxin. The structural differences may possibly explain differences in the enzymic properties between rat and bovine adrenodoxins.
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Affiliation(s)
- Y Sagara
- Department of Medical Biology, Kochi Medical School, Japan
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15
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Marg A, Kuban RJ, Behlke J, Dettmer R, Ruckpaul K. Crystallization and X-ray examination of bovine adrenodoxin. J Mol Biol 1992; 227:945-7. [PMID: 1404398 DOI: 10.1016/0022-2836(92)90235-c] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Crystals of adrenodoxin from bovine adrenocortical mitochondria were obtained by the hanging-drop vapor diffusion technique. The crystals belong to a hexagonal crystal lattice with cell parameters 172.50 A and 183.49 A. There are 12 molecules in the asymmetric unit. The crystals diffract to beyond 4.0 A resolution.
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Affiliation(s)
- A Marg
- Max-Delbrück-Centrum für molekulare Medizin, Berlin-Buch, Germany
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16
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Sagara Y, Hara T, Ariyasu Y, Ando F, Tokunaga N, Horiuchi T. Direct expression in Escherichia coli and characterization of bovine adrenodoxins with modified amino-terminal regions. FEBS Lett 1992; 300:208-12. [PMID: 1555645 DOI: 10.1016/0014-5793(92)80847-a] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Four forms of bovine adrenodoxin with modified amino-termini obtained by direct expression of cDNAs in Escherichia coli are Ad(Met1), Ad(Met-1), Ad(Met-12), and Ad(Met6). The shoulder numbers represent the site of translation initiator Met at the amino-termini. The adrenodoxins, except for Ad(Met-1), were purified from the cell lysate and the ratios of A414-to-A276 of the purified proteins were over 0.92. NADPH-cytochrome c reductase activities of the three forms of adrenodoxin in the presence of adrenodoxin reductase were the same as that of purified bovine adrenocortical adrenodoxin. However, as cytochrome P-450SCC reduction catalyzed by Ad(Met6) was about 60% of that by Ad(Met1), the contribution of the amino-terminal region for the electron transfer or binding to cytochrome P-450SCC would need to be considered.
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Affiliation(s)
- Y Sagara
- Department of Microbiology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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17
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Karaszkiewicz JW, Kalf GF. Purification and characterization of a benzene hydroxylase from rat liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1035:223-9. [PMID: 2168214 DOI: 10.1016/0304-4165(90)90121-c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
An enzyme has been purified to electrophoretic homogeneity from rat liver mitoplasts which metabolizes benzene to phenol. The enzyme has a Mr of 52,000 and requires NADPH, adrendoxin, and adrenodoxin reductase for activity. Benzene hydroxylase activity could be inhibited by carbon monoxide and SKF-525A, and by specific inhibitors of microsomal benzene metabolism. The purified enzyme also oxidized phenol to catechol. The data suggest that a cytochrome P-450 of mitochondrial origin is involved in benzene metabolism, and provide another example of a role for the mitochondrion in xenobiotic activation.
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Affiliation(s)
- J W Karaszkiewicz
- Department of Biochemistry and Molecular Biology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107
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18
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Phosphorylation of ferredoxin and regulation of renal mitochondrial 25-hydroxyvitamin D-1 α-hydroxylase activity in vitro. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84836-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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19
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Griffing GT, Holbrook M, Melby JC, Alberta J, Orme-Johnson NR. 19-Hydroxylase inhibition of adrenal mitochondrial P450 11 beta/18/19-hydroxylase by a suicide inhibitor. Am J Med Sci 1989; 298:83-8. [PMID: 2788364 DOI: 10.1097/00000441-198908000-00003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
19-Nor-deoxycorticosterone (19-nor-DOC) is a mineralocorticoid that is increased in some forms of experimental and human hypertension. The pivotal step in 19-nor-DOC biosynthesis is adrenal P450 19-hydroxylase, but this enzyme has not been clearly distinguished from P450 11 beta/18-hydroxylase. This study attempted to specifically inhibit adrenal 19-hydroxylation of deoxycorticosterone (DOC) using a suicide aromatase inhibitor, 19-acetylenic androstenedione (19-AA). Purified bovine P450 11 beta/18/19-hydroxylase was incubated with excess substrate DOC, adrenodoxin, and adrenodoxin reductase in the presence of increasing doses of the inhibitor, 19AA. 11 beta-, 18-, and 19-hydroxylation were measured by quantification of corticosterone, 18-OH-DOC, and 19-OH-DOC respectively. Measurements of these products demonstrated that 11 beta- and 18-hydroxylation was not inhibited whereas 19-hydroxylation was inhibited as manifested by decreased 19-OH-DOC formation (p less than .05). The IC50 of 19-AA was approximately 10(-12) M. The specific inhibition of 19-hydroxylation suggests that the 19-hydroxylase may be an enzyme distinct from the P450 11 beta/18-hydroxylase. This further suggests that 19-nor-DOC biosynthesis may be under independent regulation and may be amendable to specific in vivo inhibition.
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Affiliation(s)
- G T Griffing
- Evans Memorial Department of Clinical Research, University Hospital, Boston, Massachusetts 02118
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20
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Coghlan VM, Vickery LE. Expression of human ferredoxin and assembly of the [2Fe-2S] center in Escherichia coli. Proc Natl Acad Sci U S A 1989; 86:835-9. [PMID: 2644647 PMCID: PMC286572 DOI: 10.1073/pnas.86.3.835] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A cDNA fragment encoding human ferredoxin, a mitochondrial [2Fe-2S] protein, was introduced into Escherichia coli by using an expression vector based on the approach of Nagai and Thøgersen [Nagai, K. & Thøgersen, M. C. (1984) Nature (London) 309, 810-812]. Expression was under control of the lambda PL promoter and resulted in production of ferredoxin as a cleavable fusion protein with an amino-terminal fragment derived from bacteriophage lambda cII protein. The fusion protein was isolated from the soluble fraction of induced cells and was specifically cleaved to yield mature recombinant ferredoxin. The recombinant protein was shown to be identical in size to ferredoxin isolated from human placenta (13,546 Da) by NaDodSO4/PAGE and partial amino acid sequencing. E. coli cells expressing human ferredoxin were brown in color, and absorbance and electron paramagnetic resonance spectra of the purified recombinant protein established that the [2Fe-2S] center was assembled and incorporated into ferredoxin in vivo. Recombinant ferredoxin was active in steroid hydroxylations when reconstituted with cytochromes P-450scc and P-450(11) beta and exhibited rates comparable to those observed for ferredoxin isolated from human placenta. This expression system should be useful in production of native and structurally altered forms of human ferredoxin for studies of ferredoxin structure and function.
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Affiliation(s)
- V M Coghlan
- Department of Biological Chemistry, University of California, Irvine 92717
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21
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Andersen RS, Curtis JC. Electron spin resonance studies of the ovary of the rat. J Mol Struct 1988. [DOI: 10.1016/0022-2860(88)80289-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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22
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Monnier N, Defaye G, Chambaz EM. Phosphorylation of bovine adrenodoxin. Structural study and enzymatic activity. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 169:147-53. [PMID: 2824199 DOI: 10.1111/j.1432-1033.1987.tb13592.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Adrenodoxin is an iron-sulfur protein which functions as a carrier of reducing equivalents in steroid hydroxylation reactions catalyzed by specific cytochromes P-450 in steroidogenic tissues such as adrenal cortex. Purified bovine adrenocortical adrenodoxin was shown to be selectively phosphorylated upon incubation with purified cAMP-dependent protein kinase, whereas other protein kinases were ineffective. The phosphorylation reaction was completed within 45 min at 30 degrees C and resulted in the optimal incorporation of 1 mol phosphate/mol adrenodoxin. Apoadrenodoxin, lacking the iron-sulfur cluster, was also phosphorylated under similar conditions. An apparent Km of 55 microM with a Vmax of 0.3 pmol 32P incorporated min-1 mg adrenodoxin-1 was calculated. Phosphorylation resulted in a striking change in several molecular properties of adrenodoxin, such as electrophoretic behavior and hydroxyapatite affinity, thus providing the possibility of clearly separating phosphorylated from unphosphorylated adrenodoxin. In addition, phosphoadrenodoxin became refractory to mild trypsin degradation, whereas this was not the case with apoadrenodoxin. The phosphorylated site of adrenodoxin was identified as a serine residue; study of peptide products resulting from CNBr and proteolytic cleavages of phosphoadrenodoxin suggested that Ser-88 was the target of the phosphorylation reaction. The influence of phosphorylation upon adrenodoxin activity was examined using cholesterol side-chain cleavage and 11 beta-hydroxylase (11 beta) systems, reconstituted from purified components. Phosphorylation of adrenodoxin resulted in an average twofold decrease in its Km values for the two specific cytochromes P-450 involved. This effect was paralleled by a positive relationship between the degree of adrenodoxin phosphorylation and its ability to support the overall activity of reconstituted side-chain cleavage and 11 beta-hydroxylase systems. Although it remains to be examined whether adrenodoxin is phosphorylated in the intact cell, the present observations suggest that it represents a potential target in the hormonal regulation of the adrenocortical differentiated functions, especially by stimulatory agents acting through a cyclic-AMP-dependent mechanism, such as adrenocorticotropin.
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Affiliation(s)
- N Monnier
- INSERM U 244, LBIO, Département de Recherches Fondamentales CEN BP 85X, Grenoble, France
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23
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Cresnar B, Breskvar K, Hudnik-Plevnik T. Resolution and reconstitution of the NADPH-cytochrome c (P-450) reductase induced by progesterone in Rhizopus nigricans. Biochem Biophys Res Commun 1985; 133:1057-63. [PMID: 3936501 DOI: 10.1016/0006-291x(85)91243-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The NADPH-cytochrome c (P-450) reductase induced in the filamentous fungus Rhizopus nigricans as a component of 11 alpha-hydroxylase of progesterone was resolved by DEAE-cellulose chromatography into two components. One of the components is an iron-sulfur protein (rhizoporedoxin), whereas the other component is a protein with reductase activity dependent on NADPH (rhizoporedoxin reductase). As shown in the reconstitution assay, the NADPH-cytochrome c (P-450) reductase activity was restored upon combination of these two proteins.
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24
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Niranjan BG, Avadhani NG, DiGiovanni J. Formation of benzo(alpha)pyrene metabolites and DNA adducts catalyzed by a rat liver mitochondrial monooxygenase system. Biochem Biophys Res Commun 1985; 131:935-42. [PMID: 2996532 DOI: 10.1016/0006-291x(85)91329-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
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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25
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Cheng B, Hsu DK, Kimura T. Utilization of intramitochondrial membrane cholesterol by cytochrome P-450-dependent cholesterol side-chain cleavage reaction in bovine adrenocortical mitochondria: steroidogenic and non-steroidogenic pools of cholesterol in the mitochondrial inner membranes. Mol Cell Endocrinol 1985; 40:233-43. [PMID: 4007257 DOI: 10.1016/0303-7207(85)90179-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inner and outer submitochondrial membranes were prepared after disruption of malate-treated bovine adrenocortical mitochondria. It was found that a part of the endogenous cholesterol in the inner membrane (approx. 50%) was rapidly utilized by the cholesterol side-chain cleavage reaction. The utilization of cholesterol in the outer membrane, on the other hand, was inefficient and slow in spite of the fact that cholesterol concentration is higher in the outer than in the inner membrane. When the inner membrane prepared from untreated mitochondria was incubated for 20 min in the presence of a reconstituted cytochrome P-450-reducing system, the inner membrane cholesterol was depleted by approximately 70%. The half-life of the depletion reaction was 2-3 min. In addition, when the outer membrane plus the soluble fraction from the untreated mitochondria were added as a source of cholesterol to the inner membrane fraction, a marginal increase in the production of steroids was observed. From these results it is concluded that a portion of the inner membrane cholesterol can be steroidogenic, whereas the rest of the cholesterol is non-steroidogenic.
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26
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Subramanian V, Liu TN, Yeh WK, Serdar CM, Wackett LP, Gibson DT. Purification and properties of ferredoxinTOL. A component of toluene dioxygenase from Pseudomonas putida F1. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(18)89561-8] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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27
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Tobes MC, Hays SJ, Gildersleeve DL, Wieland DM, Beierwaltes WH. Adrenal cortical 11 beta-hydroxylase and side-chain cleavage enzymes. Requirement for the A- or B-pyridyl ring in metyrapone for inhibition. JOURNAL OF STEROID BIOCHEMISTRY 1985; 22:103-10. [PMID: 3871878 DOI: 10.1016/0022-4731(85)90148-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The adrenal cortical enzyme systems, 11 beta-hydroxylase, P-450 11 beta, and the side-chain cleavage complex, P-450 scc, differ only in their cytochrome P-450s. Structural modifications of metyrapone, an inhibitor of cytochrome P-450 enzyme systems, have been made to determine the requirement for the A- or B-pyridyl ring for inhibition of P-45011 beta and P-450 scc activities. Three new analogs of metyrapone (A-phenylmetyrapone, B-phenylmetyrapone and diphenylmetyrapone) were synthesized and evaluated as inhibitors using a crude, defatted bovine adrenal cortical mitochondrial preparation. Characterization of the mitochondrial preparation demonstrated: enhancement of both activities by the addition of 15.0 microM adrenodoxin, the addition of 1% ethanol decreased both activities less than 10%, and the apparent Km of deoxycorticosterone for P-45011 beta was 6.8 microM and the apparent Km of cholesterol for P-450 scc was 21.6 microM. Inhibition of P-45011 beta and P-450 scc activities with these compounds demonstrated: the B-pyridyl ring of metyrapone is required for inhibition of both activities whereas requirement for the A-ring is less stringent, and the four metyrapone analogs were more selective inhibitors of P-45011 beta activity. These studies suggest that the A-phenyl metyrapone analog is a good candidate for further development of a selective adrenocortical radiopharmaceutical.
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28
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Hattori MA, Aquilano DR, Dufau ML. An early steroidogenic defect in hormone-induced Leydig cell desensitization. ACTA ACUST UNITED AC 1984; 21:265-77. [PMID: 6548538 DOI: 10.1016/0022-4731(84)90279-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To define the nature of the lesion of the early steroidogenic pathway (prior to pregnenolone formation) in gonadotropin-induced desensitization of rat testicular Leydig cells, we evaluated cholesterol side-chain cleavage activity in isolated mitochondria by measurement of pregnenolone synthesis and [14C]isocaproic acid formation from [26-14C]cholesterol. The enzyme activity was shown to be reduced after in vivo treatment with 10 micrograms hCG when compared to that of mitochondria from control animals only when measured in the presence of limiting NADPH concentrations (100 microM). Sonication of mitochondria from control and hCG-treated rats caused complete loss of cholesterol side-chain cleavage activity. When acetone-powdered adrenal cell mitochondria were employed as the source of the enzyme, the addition of sonicated Leydig cell mitochondria from control and hCG-treated animals caused the same differences as those observed with intact Leydig cell mitochondria in the presence of low concentration of NADPH. The Km value of the adrenal enzyme for NADPH incubated with Leydig cell mitochondria increased from 0.111 mM in control to 0.37 mM after hCG, with no changes in Vmax. Moreover, cholesterol side-chain cleavage activity of adrenal mitochondria assayed in the presence of 100 microM cholesterol was progressively inhibited by increasing amounts of acetone powder from Leydig cell mitochondria of control and hCG-treated rats, with ID50 of 500 and 280 micrograms protein, respectively. The inhibiting factor was not a lipid or steroid but a heat-labile protein, with an approximate Stokes radius of 4.8 nm and an isoelectric point of 5.05 +/- 0.23 SD (n = 8). The inhibitory effect was confined to the Leydig cell mitochondrial membrane, and was not related to changes in oxidative phosphorylation. NADPH was not directly oxidized or immobilized by the mitochondrial factor, and this inhibiting substance was not adsorbed on 2',5' ADP-Sepharose 4B. These results have demonstrated that a heat-labile inhibiting protein factor is present in mitochondria from normal Leydig cells and is markedly activated or increased by hCG treatment. This substance that competitively modulates cholesterol side-chain cleavage activity could contribute to the early steroidogenic lesion, and also serve as an endogenous modulator of steroid hormone biosynthesis.
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29
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Hydroxylations in biosynthesis of bile acids. Isolation of a cytochrome P-450 from rabbit liver mitochondria catalyzing 26-hydroxylation of C27-steroids. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43166-8] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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30
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Hsu DK, Huang YY, Kimura T. Thermodynamic properties of the cholesterol transfer reaction from liposomes to cytochrome P450scc: an enthalpy-entropy compensation effect. Biochem Biophys Res Commun 1984; 118:877-84. [PMID: 6704112 DOI: 10.1016/0006-291x(84)91477-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We have investigated the thermodynamic properties of the cholesterol transfer reaction from various types of liposomes to purified steroid-free cytochrome P450scc. From the results of temperature effect on the reaction, we obtained delta G+, delta H+, and delta S+ values for the reaction with various phosphatidylcholine vesicles containing different fatty acyl chains. The plots of delta H+ against delta S+, and delta G+ against delta H+ both reveal that an enthalpy-entropy compensation effect was seen in a series of phospholipid and micellar media of cholesterol. Our beta-value of 420 degrees K is unusually high among reported values for biochemical reactions.
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31
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Huang YY, Hsu DK, Kimura T. The effect of pH on the formal reduction potential of adrenodoxin in the presence and absence of adrenodoxin reductase: the implication in the electron transfer mechanism. Biochem Biophys Res Commun 1983; 115:116-22. [PMID: 6615521 DOI: 10.1016/0006-291x(83)90977-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We have investigated the formal reduction potentials (E degrees') of adrenodoxin with and without adrenodoxin reductase in order to elucidate the mechanism of electron transfer from adrenodoxin reductase (a flavoprotein) to adrenodoxin (an iron-sulfur protein). It was found by our spectropotentiostatic method that adrenodoxin showed no variation of E degrees' at different pH's in the absence of adrenodoxin reductase. The average E degrees' was -252 +/- 2 mV in the pH range between 6.0 and 8.3. In the presence of adrenodoxin reductase, adrenodoxin exhibited, on the other hand, a pH dependence of E degrees' at pH higher than 7.2 with a slope of -59 mV per pH unit: Adrenodoxin molecule possesses one protonation site with a pKa of 7.2. Cyclic voltammograms of adrenodoxin additionally revealed that the reoxidation reaction of reduced adrenodoxin is very slow in the absence of adrenodoxin reductase, but that it is readily reoxidized in the presence of adrenodoxin reductase.
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32
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The complete amino acid sequence of rabbit phenobarbital-induced liver microsomal cytochrome P-450. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32605-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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33
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19 P-450 Oxygenases in Lipid Transformation. ACTA ACUST UNITED AC 1983. [DOI: 10.1016/s1874-6047(08)60317-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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34
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Adrenodoxin biosynthesis by bovine adrenal cells in monolayer culture. Induction by adrenocorticotropin. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)33371-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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35
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Hintz MJ, Mock DM, Peterson LL, Tuttle K, Peterson JA. Equilibrium and kinetic studies of the interaction of cytochrome P-450cam and putidaredoxin. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(19)45384-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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36
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Kido T, Kimura T. Stimulation by calcium and other cations of the cholesterol binding to steroid-free cytochrome P-450scc purified from bovine adrenocortical mitochondria: the implication of ACTH-mediated calcium homeostasis on the cholesterol availability. ENDOCRINE RESEARCH COMMUNICATIONS 1982; 9:9-24. [PMID: 6284476 DOI: 10.1080/07435808209045749] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
By utilizing purified cytochrome P-450scc from bovine adrenocortical mitochondria and cholesterol-containing dioleoylglycerophosphocholine liposomes, we have demonstrated a dramatic stimulation (2-3 fold) of cholesterol binding to the steroid-free cytochrome by Ca++. We theorize that ACTH modulates the increase of intracellular Ca++ concentration resulting in the increase of the cholesterol availability to the mitochondrial cytochrome.
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37
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Kido T, Yamakura F, Kimura T. The transfer of cholesterol and hydroxycholesterol derivatives from liposome to soluble cytochrome P-450 scc. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 666:370-81. [PMID: 7326249 DOI: 10.1016/0005-2760(81)90296-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We have studied the cholesterol-binding reaction with purified steroid-free cytochrome P-450scc. By mixing an aqueous solution of cholesterol-, pregnenolone- and progesterone-free cytochrome with cholesterol-containing liposomes, the low to high spin conversion of the hemoprotein was observed spectrophotometrically and by electron spin resonance spectroscopy. When the binding rates were compared at a fixed molar heme: cholesterol ratio of 1 : 1, 20 mol% cholesterol-dioleoylglycerophosphocholine liposomes react with the cytochrome at a faster rate than 50 mol% cholesterol-dimyristoylglycerophosphocholine liposomes, indicating that the availability of cholesterol molecules in an unsaturated membrane is better than in a saturated membrane. When the number of cholesterol-dioleoylglycerophosphocholine liposomes was increased, the cholesterol-binding rates increased markedly. These results imply that the collision of the liposomes with the soluble hemoprotein molecules plays an important role in the binding reaction under our experimental conditions. The binding reaction was found to be temperature-dependent with a refractive temperature at near 20 degrees C. From the comparison of the binding abilities among cholesterol derivatives tested, wer conclude that the alpha-face of the A-B transfused rings and the portion of the hydrocarbon side-chain of cholesterol are important for the binding. Additionally, polar derivatives had faster rates than non-polar steroids in structurally homologous series.
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38
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Yamakura F, Kido T, Kimura T. Characterization of cytochrome P-450scc-containing liposomes. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 649:343-54. [PMID: 7317404 DOI: 10.1016/0005-2736(81)90424-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Purified cytochrome P450scc from bovine adrenocortical mitochondria was incorporated into liposomes by the cholate-dilution method utilizing either dialysis or Sephadex gel filtration. Among synthetic phospholipids tested, dioleoylglycerophosphocholine showed the best stability during the incorporation of P450scc into liposomes. A maximum amount of heme was incorporated into liposomes at a molar ratio of phospholipid to the cytochrome of approx. 200. When P450scc was incorporated into the dioleoylglycerophosphocholine liposomes by the cholate-filtration method, the P450scc-containing liposomes showed two major populations on the elution pattern of the Sepharose 4B gel filtration, and were seen at a diameter of 200-600 A and its aggregated forms. When the cytochrome was incorporated into dioleoylglycerophosphocholine liposomes or cholesterol-free adrenocortical mitochondrial liposomes, P450scc was less stable than P450scc in aqueous solution. Cholesterol or adrenodoxin markedly stabilized the liposomal P450scc. Liposomal P450scc required cholesterol for its optimum reduction with adrenodoxin, adrenodoxin reductase, and NADPH in the presence of CO. About 70% of the total heme in the dioleoylglycerophosphocholine liposomes was reduced by the enzymatic reduction in the presence of cholesterol, indicating that 70% of the total molecules are exposed to the surface of the outer monolayer. In order to see the location of the heme in membrane, the dioleoylglycerophosphocholine-liposomal P450scc was subjected to p-chloromercuriphenyl sulfonic acid treatment. This reagent destroyed the liposomal P450scc. These results suggest that the heme is located in the proximity of the p-chloromercuriphenyl sulfonic acid reacting sites which are exposed to the surface, or located on the vincinity of polar heads of the membrane.
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39
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Kido T, Kimura T. Stimulation of cholesterol binding to steroid-free cytochrome P-450scc by poly(L-lysine). The implication in functions of labile protein factor for adrenocortical steroidogenesis. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68880-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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40
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Bicknell-Brown E, Lim BT, Kimura T. Laser Raman spectroscopy of adrenal iron-sulfur apoprotein: the anomalous tyrosine residue at position 82. Biochem Biophys Res Commun 1981; 101:298-305. [PMID: 7284006 DOI: 10.1016/s0006-291x(81)80044-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Kimura T. ACTH stimulation on cholesterol side chain cleavage activity of adrenocortical mitochondria. Transfer of the stimulus from plasma membrane to mitochondria. Mol Cell Biochem 1981; 36:105-22. [PMID: 6264282 DOI: 10.1007/bf02354909] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Adrenocortical mitochondrial cholesterol side chain cleavage reactions are regulated by the influence of pituitary ACTH. The mechanism of the stimulation involves adenyl cyclase, cAMP-dependent protein kinase, cholesterol esterase, and ribosomal labile protein synthesis. Through these reactions the stimulus reaches the mitochondrial side chain cleavage enzyme system. In this review article, the current implications on the stimulus transfer from the plasma membrane to the mitochondrial inner membrane are summarized. In particular the availability of cholesterol to P-450scc was discussed in terms of the distribution of cholesterol molecules in the membranes.
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Strauss JF, Schuler LA, Rosenblum MF, Tanaka T. Cholesterol metabolism by ovarian tissue. ADVANCES IN LIPID RESEARCH 1981; 18:99-157. [PMID: 6275662 DOI: 10.1016/b978-0-12-024918-3.50009-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Hanukoglu I, Jefcoate CR. Mitochondrial cytochrome P-450scc. Mechanism of electron transport by adrenodoxin. J Biol Chem 1980; 255:3057-61. [PMID: 6766943 DOI: 10.1016/s0021-9258(19)85851-9] [Citation(s) in RCA: 114] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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Kido T, Kimura T. The formation of binary and ternary complexes of cytochrome P-450scc with adrenodoxin and adrenodoxin reductase.adrenodoxin complex. The implication in ACTH function. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(19)86389-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Seybert D, Lancaster J, Lambeth J, Kamin H. Participation of the membrane in the side chain cleavage of cholesterol. Reconstitution of cytochrome P-450scc into phospholipid vesicles. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(19)86433-5] [Citation(s) in RCA: 84] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Adrenal cortex mitochondrial cytochrome P-450 specific to cholesterol side chain cleavage reaction. Spectral changes induced by detergents, alcohols, amines, phospholipids, steroid hydroxylase inhibitors, and steroid substrates, and conditions for adrenodoxin binding to the cytochrome. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(19)86901-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Topological studies of the steroid hydroxylase complexes in bovine adrenocortical mitochondria. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)34636-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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