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Gonzalez L, Chau-Duy Tam Vo S, Faivre B, Pierrel F, Fontecave M, Hamdane D, Lombard M. Activation of Coq6p, a FAD Monooxygenase Involved in Coenzyme Q Biosynthesis, by Adrenodoxin Reductase/Ferredoxin. Chembiochem 2024; 25:e202300738. [PMID: 38141230 DOI: 10.1002/cbic.202300738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/22/2023] [Accepted: 12/23/2023] [Indexed: 12/25/2023]
Abstract
Adrenodoxin reductase (AdxR) plays a pivotal role in electron transfer, shuttling electrons between NADPH and iron/sulfur adrenodoxin proteins in mitochondria. This electron transport system is essential for P450 enzymes involved in various endogenous biomolecules biosynthesis. Here, we present an in-depth examination of the kinetics governing the reduction of human AdxR by NADH or NADPH. Our results highlight the efficiency of human AdxR when utilizing NADPH as a flavin reducing agent. Nevertheless, akin to related flavoenzymes such as cytochrome P450 reductase, we observe that low NADPH concentrations hinder flavin reduction due to intricate equilibrium reactions between the enzyme and its substrate/product. Remarkably, the presence of MgCl2 suppresses this complex kinetic behavior by decreasing NADPH binding to oxidized AdxR, effectively transforming AdxR into a classical Michaelis-Menten enzyme. We propose that the addition of MgCl2 may be adapted for studying the reductive half-reactions of other flavoenzymes with NADPH. Furthermore, in vitro experiments provide evidence that the reduction of the yeast flavin monooxygenase Coq6p relies on an electron transfer chain comprising NADPH-AdxR-Yah1p-Coq6p, where Yah1p shuttles electrons between AdxR and Coq6p. This discovery explains the previous in vivo observation that Yah1p and the AdxR homolog, Arh1p, are required for the biosynthesis of coenzyme Q in yeast.
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Affiliation(s)
- Lucie Gonzalez
- Laboratoire de Chimie des Processus Biologiques, Collège de France, Sorbonne Université, CNRS UMR8229, PSL Research University, Sorbonne Université, 11 place Marcelin Berthelot, 75 005, Paris, France
| | - Samuel Chau-Duy Tam Vo
- Laboratoire de Chimie des Processus Biologiques, Collège de France, Sorbonne Université, CNRS UMR8229, PSL Research University, Sorbonne Université, 11 place Marcelin Berthelot, 75 005, Paris, France
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Bruno Faivre
- Laboratoire de Chimie des Processus Biologiques, Collège de France, Sorbonne Université, CNRS UMR8229, PSL Research University, Sorbonne Université, 11 place Marcelin Berthelot, 75 005, Paris, France
| | - Fabien Pierrel
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000, Grenoble, France
| | - Marc Fontecave
- Laboratoire de Chimie des Processus Biologiques, Collège de France, Sorbonne Université, CNRS UMR8229, PSL Research University, Sorbonne Université, 11 place Marcelin Berthelot, 75 005, Paris, France
| | - Djemel Hamdane
- Laboratoire de Chimie des Processus Biologiques, Collège de France, Sorbonne Université, CNRS UMR8229, PSL Research University, Sorbonne Université, 11 place Marcelin Berthelot, 75 005, Paris, France
- Institut de Biologie Paris-Seine, Biology of Aging and Adaptation, UMR 8256, Sorbonne Université, 7 quai Saint-Bernard, 75 252, Paris, France
| | - Murielle Lombard
- Laboratoire de Chimie des Processus Biologiques, Collège de France, Sorbonne Université, CNRS UMR8229, PSL Research University, Sorbonne Université, 11 place Marcelin Berthelot, 75 005, Paris, France
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McKay TB, Priyadarsini S, Karamichos D. Sex Hormones, Growth Hormone, and the Cornea. Cells 2022; 11:cells11020224. [PMID: 35053340 PMCID: PMC8773647 DOI: 10.3390/cells11020224] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/03/2022] [Accepted: 01/07/2022] [Indexed: 12/31/2022] Open
Abstract
The growth and maintenance of nearly every tissue in the body is influenced by systemic hormones during embryonic development through puberty and into adulthood. Of the ~130 different hormones expressed in the human body, steroid hormones and peptide hormones are highly abundant in circulation and are known to regulate anabolic processes and wound healing in a tissue-dependent manner. Of interest, differential levels of sex hormones have been associated with ocular pathologies, including dry eye disease and keratoconus. In this review, we discuss key studies that have revealed a role for androgens and estrogens in the cornea with focus on ocular surface homeostasis, wound healing, and stromal thickness. We also review studies of human growth hormone and insulin growth factor-1 in influencing ocular growth and epithelial regeneration. While it is unclear if endogenous hormones contribute to differential corneal wound healing in common animal models, the abundance of evidence suggests that systemic hormone levels, as a function of age, should be considered as an experimental variable in studies of corneal health and disease.
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Affiliation(s)
- Tina B. McKay
- Department of Cell Biology, University of Oklahoma Health Sciences, Oklahoma City, OK 73104, USA;
| | | | - Dimitrios Karamichos
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
- Department of Pharmaceutical Sciences, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
- Correspondence: ; Tel.: +1-817-735-2101
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McLean KJ, Scrutton NS, Munro AW. Kinetic, spectroscopic and thermodynamic characterization of the Mycobacterium tuberculosis adrenodoxin reductase homologue FprA. Biochem J 2003; 372:317-27. [PMID: 12614197 PMCID: PMC1223410 DOI: 10.1042/bj20021692] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2002] [Revised: 02/28/2003] [Accepted: 03/03/2003] [Indexed: 11/17/2022]
Abstract
The genome sequence of the pathogenic bacterium Mycobacterium tuberculosis revealed numerous cytochrome P450 enzymes, which require accessory redox enzymes for catalytic function (ferredoxin reductase and ferredoxin). The most likely ferredoxin reductase is encoded by fprA, and its structure resembles eukaryotic adrenodoxin reductases. We have cloned, expressed and purified the flavoenzyme product of the fprA gene in Escherichia coli. FprA reduces various electron acceptors using either NADPH or NADH as the electron donor, but discriminates in favour of NADPH (apparent K (m) for NADH=50.6+/-3.1 microM; NADPH=4.1+/-0.3 microM from ferricyanide reduction experiments). Stopped-flow studies of reduction of the FprA FAD by NADPH demonstrate increased flavin reduction rate at low NADPH concentration (<200 microM), consistent with the presence of a second, kinetically distinct and inhibitory, pyridine nucleotide-binding site, similar to that identified in human cytochrome P450 reductase [Gutierrez, Lian, Wolf, Scrutton and Roberts (2001) Biochemistry 40, 1964-1975]. Flavin reduction by NADH is slower than with NADPH and displays hyperbolic dependence on NADH concentration [maximal reduction rate ( k (red))=25.4+/-0.7 s(-1), apparent K (d)=42.9+/-4.6 microM]. Flavin reoxidation by molecular oxygen is more rapid for NADH-reduced enzyme. Reductive titrations show that the enzyme forms a species with spectral characteristics typical of a neutral (blue) FAD semiquinone only on reduction with NADPH, consistent with EPR studies. The second order dependence of semiquinone formation on the concentration of FprA indicates a disproportionation reaction involving oxidized and two-electron-reduced FprA. Titration of FprA with dithionite converts oxidized FAD into the hydroquinone form; the flavin semiquinone is not populated under these conditions. The midpoint reduction potential for the two electron couple is -235+/-5 mV (versus the normal hydrogen electrode), similar to that for adrenodoxin reductase (-274 mV). Our data provide a thermodynamic and transient kinetic framework for catalysis by FprA, and complement recent spectrophotometric and steady-state studies of the enzyme [Fischer, Raimondi, Aliverti and Zanetti (2002) Eur. J. Biochem. 269, 3005-3013].
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Affiliation(s)
- Kirsty J McLean
- Department of Biochemistry, University of Leicester, The Adrian Building, University Road, UK
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4
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Okuda KI. Liver mitochondrial P450 involved in cholesterol catabolism and vitamin D activation. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)41189-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
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5
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Hagenfeldt Y, Pedersen JI, Björkhem I. Properties of guinea-pig kidney 25-hydroxyvitamin D3 1 alpha-hydroxylase assayed by isotope dilution-mass spectrometry. Biochem J 1988; 250:521-6. [PMID: 3281665 PMCID: PMC1148886 DOI: 10.1042/bj2500521] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
1. A highly specific and accurate method based on isotope dilution-mass spectrometry was used for characterization of the renal 25-hydroxyvitamin D3 1 alpha-hydroxylase in untreated guinea pigs with a normal vitamin D status. In previous work, the properties of the enzyme had been determined in rachitic animals only. 2. With intact mitochondria, the reaction required the presence of citric acid-cycle intermediates. The uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone had an inhibitory effect on the isocitrate-supported reaction, indicating that energy-dependent transhydrogenation is of importance. Mitochondrial respiratory-chain inhibitors (cyanide, rotenone, antimycin A) had no effect on the hydroxylation. CO had an inhibitory effect, suggesting participation of a species of cytochrome P-450 in the reaction. A fraction solubilized from mitochondria by cholate became catalytically active in 1 alpha-hydroxylation of 25-hydroxyvitamin D3 after addition of ferredoxin and ferredoxin reductase. The isocitrate-supported reaction catalysed by crude mitochondria had an apparent Km of about 1 microM. 3. An atmosphere containing 50% O2 was found to be necessary for optimal activity. It is thus possible that O2 may be a limiting factor under normal conditions in vivo. 4. The results demonstrate that the mammalian renal 25-hydroxyvitamin D3 1 alpha-hydroxylase is a cytochrome P-450-dependent mixed-function oxidase with properties similar to those previously reported for the same enzyme system in chicken. The present assay and animal system seem to be suitable for further studies on the mechanism of regulation of the mammalian renal 25-hydroxyvitamin D3 1 alpha-hydroxylase under conditions when the vitamin D status is normal.
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Affiliation(s)
- Y Hagenfeldt
- Department of Clinical Chemistry, Huddinge Hospital, Stockholm, Sweden
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6
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Hanukoglu I, Gutfinger T, Haniu M, Shively JE. Isolation of a cDNA for adrenodoxin reductase (ferredoxin-NADP+ reductase). Implications for mitochondrial cytochrome P-450 systems. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 169:449-55. [PMID: 3691502 DOI: 10.1111/j.1432-1033.1987.tb13632.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Using specific antibodies against adrenodoxin reductase (AR), we screened lambda gt11 cDNA expression libraries constructed from bovine adrenal cortex mRNA, and isolated several putative clones coding for this enzyme. Concurrently we determined the amino acid sequences of fragments from it. A deoxyinosine-containing oligonucleotide probe, generated for one of the sequences, reacted specifically with one of the cloned cDNAs of about 1600 base pairs. The codon sequence of this cDNA matched the peptide sequences, further confirming its identity as a copy of AR mRNA. RNA blot analysis indicates that in the adrenal cortex and corpus luteum there is only one major mRNA (approximately 2000 bp) for AR. The levels of this mRNA are at least 40-fold lower in the liver and kidney which are also known to contain in homologue of AR. As compared to adrenodoxin and cytochrome P-450scc mRNAs, AR mRNA levels in the adrenal cortex appear to be about 10-fold lower. Southern blot analysis of bovine and human genomic DNAs reveals that in both of these species there is only one gene for AR. These results indicate that only a single reductase serves the different mitochondrial P-450 systems in steroidogenic tissues.
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Affiliation(s)
- I Hanukoglu
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
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Isolation and characterization of pig kidney mitochondrial ferredoxin:NADP+ oxidoreductase. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67140-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Saarem K, Pedersen JI. 25-Hydroxylation of 1 alpha-hydroxyvitamin D-3 in rat and human liver. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 840:117-26. [PMID: 3995079 DOI: 10.1016/0304-4165(85)90168-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
1 alpha-Hydroxyvitamin D-3 25-hydroxylase activity was measured in subcellular fractions of rat and human liver. The formation of 1,25-dihydroxyvitamin D-3 was determined by high pressure liquid chromatography. In rat liver 1 alpha-hydroxyvitamin D-3 25-hydroxylase activities were found in the purified nuclei, the heavy mitochondrial fraction and the microsomal fraction. The enrichment of 25-hydroxylase activity was highest in the heavy mitochondrial fraction. With this fraction a minimum amount (about 0.5 mg) of protein was required before formation of 1,25-dihydroxyvitamin D-3 could be detected. Above this amount the reaction was linear with amount of protein up to at least 2 mg/ml. The reaction was also linear with time up to 60 min. An apparent Km value of 2 X 10(-5) M was found. The mitochondrial 25-hydroxylase was stimulated by addition of cytosolic protein or bovine serum albumin. The degree of stimulation was dependent on the amount of mitochondrial protein present in the incubation mixture. Maximal stimulation was seen with 0.2 mg/ml of either protein in the presence of 0.5 mg mitochondrial protein. The stimulating effect remained after heating the protein for 5 min at 100 degrees C. The cytosolic protein did not stimulate a reconstituted mitochondrial 1 alpha-hydroxyvitamin D-3 25-hydroxylase. The mitochondrial vitamin D-3 25-hydroxylase was inhibited both by cytosolic protein and by bovine serum albumin. Human liver revealed only one 1 alpha-hydroxyvitamin D-3 25-hydroxylase activity located to the heavy mitochondrial fraction. The results are in agreement with previous studies on the localization of vitamin D-3 25-hydroxylase in rat and human liver. The difference in localization of the 25-hydroxylase between rat and human liver implies that studies on the regulation of the microsomal 25-hydroxylase in rat liver may not be relevant to the situation in human liver.
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Moreno SN, Mason RP, Docampo R. Ca2+ and Mg2+-enhanced reduction of arsenazo III to its anion free radical metabolite and generation of superoxide anion by an outer mitochondrial membrane azoreductase. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)42645-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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10
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Reduction of nifurtimox and nitrofurantoin to free radical metabolites by rat liver mitochondria. Evidence of an outer membrane-located nitroreductase. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(20)82140-1] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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11
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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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Björkhem I, Fausa O, Hopen G, Oftebro H, Pedersen JI, Skrede S. Role of the 26-hydroxylase in the biosynthesis of bile acids in the normal state and in cerebrotendinous xanthomatosis. An in vivo study. J Clin Invest 1983; 71:142-8. [PMID: 6848555 PMCID: PMC436846 DOI: 10.1172/jci110742] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
On the basis of different in vitro studies, we have previously suggested that the basic metabolic defect in the rare inherited disease cerebrotendinous xanthomatosis (CTX) is a lack of a hepatic mitochondrial C27-steroid 26-hydroxylase, involved in the normal biosynthesis of bile acids (1980. J. Clin. Invest. 65: 1418-1430; 1981. J. Lipid Res. 22: 191-200; 22: 632-640). In the present work, this hypothesis was tested in vivo. One patient with CTX and two control subjects received intravenously a mixture of [4-14C]7 alpha-hydroxy-4-cholesten-3-one and [6 beta-3H]7 alpha,26-dihydroxy-4-cholesten-3-one, steroids believed to be important precursors of chenodeoxycholic acid. The ratio between 14C and 3H in cholic acid and chenodeoxycholic acid isolated from bile of the CTX-patient was approximately 1/40 and 1/60 of those of the control subjects, respectively. Another patient with CTX and one control subject received a mixture of [4-14C]5 beta-cholestane-3 alpha,7 alpha-diol and [1,2-3H]5 beta-cholestane-3 alpha,7 alpha,26-triol, both possible precursors to chenodeoxycholic acid. In this case the 14C/3H ratio in cholic acid and chenodeoxycholic acid from the patient with CTX was 1/10 and 1/15, respectively, compared with that of the control subject. The most likely explanation for these findings is that very little of the 14C-precursors, i.e. without a 26-hydroxyl group, can be converted into cholic acid and chenodeoxycholic acid because of a defect of the 26-hydroxylase step. The results obtained are in accord with our previous findings in vitro. The results further underline the importance of the 26-hydroxylase pathway in the normal biosynthesis of cholic acid and chenodeoxycholic acid in man.
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Oftebro H, Saarem K, Björkhem I, Pedersen JI. Side chain hydroxylation of C27-steroids and vitamin D3 by a cytochrome P-450 enzyme system isolated from human liver mitochondria. J Lipid Res 1981. [DOI: 10.1016/s0022-2275(20)37318-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Oftebro H, Björkhem I, Skrede S, Schreiner A, Pederson JI. Cerebrotendinous xanthomatosis: a defect in mitochondrial 26-hydroxylation required for normal biosynthesis of cholic acid. J Clin Invest 1980; 65:1418-30. [PMID: 7410549 PMCID: PMC371480 DOI: 10.1172/jci109806] [Citation(s) in RCA: 195] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Oxidation of side chain of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol was studied in a patient with cerebrotendinous xanthomatosis (CTX) and in control subjects, using various subcellular fractions of liver homogenate and a method based on isotope dilution-mass spectrometry. In the control, 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol was converted into 5 beta-cholestane-3 alpha,7 alpha,12 alpha,26-tetrol and 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid by the mitochondrial fraction, and into 5 beta-cholestane-3 alpha,7 alpha,12 alpha,-25-tetrol by the microsomal fraction. In the CTX patient, liver mitochondria were completely devoid of 26-hydroxylase activity. The same mitochondrial fraction catalyzed 25-hydroxylation of vitamin D3. The microsomal fraction of liver of the subject with CTX contained more than 50-fold the normal amount of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol. The basic metabolid defect in CTX appears to be a lack of the mitochondrial 26-hydroxylase. The excretion in the bile of 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol and 5 beta-cholestane-3 alpha,7 alpha,12 alpha,24 alpha,25-pentol observed in CTX patients may be secondary to the accumulation of the major substrate for the 26-hydroxylase, i. e., 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol, and exposure of this substrate to the normally less active microsomal 25-and 24-hydroxylases. It is concluded that the major pathway in the biosynthesis of cholic acid in human liver involves a mitochondrial C27-steroid 26-hydroxylation.
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Størmer FC, Pedersen JI. Formation of 4-hydroxyochratoxin A from ochratoxin A by rat liver microsomes. Appl Environ Microbiol 1980; 39:971-5. [PMID: 7396488 PMCID: PMC291461 DOI: 10.1128/aem.39.5.971-975.1980] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Hydroxyochratoxin A was isolated and identified from the urine of rats after injection with ochratoxin A. By incubating ochratoxin A with rat liver microsomes and reduced nicotinamide adenine dinucleotide phosphate, one major (90%) and two minor metabolites, more polar than ochratoxin A, were formed. Thin-layer chromatography revealed that the major metabolite had Rf values identical to those of hydroxyochratoxin A in six different solvent systems. Formation of the metabolites in vitro was inhibited by carbon monoxide and by metyrapone, and the rate of formation increased after pretreatment of the rats with phenobarbital. A type I spectrum appeared upon binding of ochratoxin A to microsomes with a spectral dissociation constant (Ks) of 37.6 microM. These findings strongly suggest the involvement of a cytochrome P-450 in the hydroxylation of ochratoxin A by rat liver microsomes. Apparent Km and Vmax values for the formation of hydroxyochratoxin A were determined to 50 microM and 5.5 nmol/mg of protein per h, respectively.
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18
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Oftebro H, Størmer F, Pedersen J. The presence of an adrenodoxin-like ferredoxin and cytochrome P-450 in brain mitochondria. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30009-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Pedersen JI, Holmberg I, Björkhem I. Reconstitution of vitamin D3 25-hydroxylase activity with a cytochrome P-450 preparation from rat liver mitochondria. FEBS Lett 1979; 98:394-8. [PMID: 217740 DOI: 10.1016/0014-5793(79)80225-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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20
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Pedersen JI, Saarem K. Rat liver mitochondrial cytochrome P-450--A C27-steroid 26-hydroxylase. JOURNAL OF STEROID BIOCHEMISTRY 1978; 9:1165-8. [PMID: 745412 DOI: 10.1016/0022-4731(78)90007-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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21
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Saarem K, Pedersen JI, Tollersrud S. Soluble 25-hydroxyvitamin D3-1 alpha-hydroxylase from kidney mitochondria of rachitic pigs. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1978; 61:485-90. [PMID: 318387 DOI: 10.1016/0305-0491(78)90039-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
1. Mitochondria isolated from the kidneys of rachitic pigs have been shown to contain an active 25-hydroxyvitamin D3-1 alpha-hydroxylase. From these mitochondria a cytochrome P-450 has been solubilized with a specific content of 0.02-0.04 nmol/mg protein. 2. In the presence of a bovine adrenal NADPH-ferredoxin reductase, bovine adrenal ferredoxin and NADPH, the cytochrome P-450 supported the formation of 1,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3. 3. The hydroxylation reaction was linear with time up to 40 min, and with the amount of enzyme up to 0.03 nmol cytochrome P-450. The pH optimum for the reaction was 7.4, and the apparent Km was 3 x 10(-10) mol/mg protein. 4. The results show that 25-hydroxyvitamin D3 is metabolized in mammals by the same enzyme system as has been demonstrated in birds.
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Affiliation(s)
- K Saarem
- Institute for Nutrition Research, School of Medicine, University of Oslo, Norway
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