- Functional interactions of adrenodoxin with several human mitochondrial cytochrome P450 enzymes
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Seven of the 57 human cytochrome P450 (P450) enzymes are mitochondrial and carry out important reactions with steroids and vitamins A and D. These seven P450s utilize an electron transport chain that includes NADPH, NADPH-adrenodoxin reductase (AdR), and adrenodoxin (Adx) instead of the diflavin NADPH-P450 reductase (POR) used by the other P450s in the endoplasmic reticulum. Although numerous studies have been published involving mitochondrial P450 systems, the experimental conditions vary considerably. We compared human Adx and bovine Adx, a commonly used component, and found very similar catalytic activities in reactions catalyzed by human P450s 11B2, 27A1, and 27C1. Binding constants of 6–200 nM were estimated for Adx binding to these P450s using microscale thermophoresis. All P450 catalytic reactions were saturated at 10 μM Adx, and higher concentrations were not inhibitory up to at least 50 μM. Collectively these studies demonstrate the tight binding of Adx (both human and bovine) to AdR and to several mitochondrial P450s and provide guidance for optimization of Adx-dependent P450 reactions.
- Barckhausen, Ian R.,Child, Stella A.,Glass, Sarah M.,Goldfarb, Margo H.,Guengerich, F. Peter,Reddish, Michael J.
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- Substrate specificity and subcellular localization of the aldehyde-Alcohol redox-Coupling reaction in carp cones
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Our previous study suggested the presence of a novel conespecific redox reaction that generates 11-cis-retinal from 11-cisretinol in the carp retina. This reaction is unique in that 1) both 11-cis-retinol and all-trans-retinal were required to produce 11-cis-retinal; 2) together with 11-cis-retinal, all-trans-retinol was produced at a 1:1 ratio; and 3) the addition of enzyme cofactors such as NADP(H) was not necessary. This reaction is probably part of the reactions in a cone-specific retinoid cycle required for cone visual pigment regeneration with the use of 11-cis-retinol supplied from Mueller cells. In this study, using purified carp cone membrane preparations, we first confirmed that the reaction is a redox-coupling reaction between retinals and retinols. We further examined the substrate specificity, reaction mechanism, and subcellular localization of this reaction. Oxidation was specific for 11-cis-retinol and 9-cis-retinol. In contrast, reduction showed low specificity: many aldehydes, including all-trans-, 9-cis-, 11-cis-, and 13-cis-retinals and even benzaldehyde, supported the reaction. On the basis of kinetic studies of this reaction (aldehyde-alcohol redox-coupling reaction), we found that formation of a ternary complex of a retinol, an aldehyde, and a postulated enzyme seemed to be necessary, which suggested the presence of both the retinol- and aldehydebinding sites in this enzyme. A subcellular fractionation study showed that the activity is present almost exclusively in the cone inner segment. These results suggest the presence of an effective production mechanism of 11-cis-retinal in the cone inner segment to regenerate visual pigment.
- Sato, Shinya,Fukagawa, Takashi,Tachibanaki, Shuji,Yamano, Yumiko,Wada, Akimori,Kawamura, Satoru
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p. 36589 - 36597
(2014/01/17)
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- Synthesis of ring-oxidized retinoids as substrates of mouse class I alcohol dehydrogenase (ADH1)
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Ring-oxidized retinoids have been synthesized stereoselectively using the Stille cross-coupling reaction. Kinetic constants of mouse class I alcohol dehydrogenase (ADH1) with these retinoids were determined.
- Dominguez, Marta,Alvarez, Rosana,Martras, Silvia,Farres, Jaume,Pares, Xavier,De Lera, Angel R.
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p. 3368 - 3373
(2007/10/03)
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- Iron(III)Porphinate/H2O2-Mediated Conversion of All-(E)-Retinol
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The reaction of hydrogen peroxide with all-(E)-retinol (1) catalyzed by (meso-tetraphenylporphinato)iron(III) led to the formation of 4-hydroxyretinol (2), 4-oxoretinol (3), 5,8-epoxyretinol (4), 5,6-epoxyretinol (5), 3-dehydroretinol (6), all-(E)- and 12-(Z)-retroretinol (7/7a) as well as all-(E)- and 12-(Z)-anhydroretinol (8/8a) as major non-volatile products.The conversion products were characterized by comparison of their chromatographic (HPLC) and spectroscopic data (UV; MS; 1H and 13C NMR) with those of synthesized reference compounds.The observed product formation supports the hypothesis of a C4 centered radical as the key intermediate of all-(E)-retinol conversion. - Keywords: 5,6- and 5,8-Epoxyretinol, 4-Hydroxyretinol, 4-Oxoretinol, Retinol Conversion
- Waldmann, Doris,Koenig, Thorsten,Schreier, Peter
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p. 589 - 594
(2007/10/02)
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