- CYP26C1 is a hydroxylase of multiple active retinoids and interacts with cellular retinoic acid binding proteins
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The clearance of retinoic acid (RA) and its metabolites is believed to be regulated by the CYP26 enzymes, but the specific roles of CYP26A1, CYP26B1, and CYP26C1 in clearing active vitamin A metabolites have not been defined. The goal of this study was to
- Zhong, Guo,Ortiz, David,Zelter, Alex,Nath, Abhinav,Isoherranen, Nina
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p. 489 - 503
(2018/04/12)
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- Catalytic activities of tumor-specific human cytochrome P450 CYP2W1 toward endogenous substrates
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CYP2W1 is a recently discovered human cytochrome P450 enzyme with a distinctive tumor-specific expression pattern. We show here that CYP2W1 exhibits tight binding affinities for retinoids, which have lownanomolar binding constants, andmuch poorer binding constants in the micromolar range for four other ligands. CYP2W1 converts alltrans retinoic acid (atRA) to 4-hydroxy atRA and all-Trans retinol to 4-OH all-Trans retinol, and it also oxidizes retinal. The enzyme much less efficiently oxidizes 17b-estradiol to 2-hydroxy-(17b)-estradiol and farnesol to a monohydroxylated product; arachidonic acid is, at best, a negligible substrate. These findings indicate that CYP2W1 probably plays an important role in localized retinoid metabolism that may be intimately linked to its involvement in tumor development.
- Zhao, Yan,Wan, Debin,Yang, Jun,Hammock, Bruce D.,De Montellano, Paul R. Ortiz
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p. 771 - 780
(2017/02/10)
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- Stereoselective formation and metabolism of 4-hydroxy-retinoic acid enantiomers by cytochrome p450 enzymes
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All-trans-retinoic acid (atRA), the major active metabolite of vitamin A, plays a role in many biological processes, including maintenance of epithelia, immunity, and fertility and regulation of apoptosis and cell differentiation. atRA is metabolized mainly by CYP26A1, but other P450 enzymes such as CYP2C8 and CYP3As also contribute to atRA 4-hydroxylation. Although the primary metabolite of atRA, 4-OH-RA, possesses a chiral center, the stereochemical course of atRA 4-hydroxylation has not been studied previously. (4S)- and (4R)-OH-RA enantiomers were synthesized and separated by chiral column HPLC. CYP26A1 was found to form predominantly (4S)-OH-RA. This stereoselectivity was rationalized via docking of atRA in the active site of a CYP26A1 homology model. The docked structure showed a well defined niche for atRA within the active site and a specific orientation of the β-ionone ring above the plane of the heme consistent with stereoselective abstraction of the hydrogen atom from the pro-(S)-position. In contrast to CYP26A1, CYP3A4 formed the 4-OH-RA enantiomers in a 1:1 ratio and CYP3A5 preferentially formed (4R)-OH-RA. Interestingly, CYP3A7 and CYP2C8 preferentially formed (4S)-OH-RA from atRA. Both (4S)- and (4R)-OH-RA were substrates of CYP26A1 but (4S)-OH-RA was cleared 3-fold faster than (4R)-OH-RA. In addition, 4-oxo-RA was formed from (4R)-OH-RA but not from (4S)-OH-RA by CYP26A1. Overall, these findings show that (4S)-OH-RA is preferred(4R)-OH-RA by the enzymes regulating atRA homeostasis. The stereoselectivity observed in CYP26A1 function will aid in better understanding of the active site features of the enzyme and the disposition of biologically active retinoids.
- Shimshoni, Jakob A.,Roberts, Arthur G.,Scian, Michele,Topletz, Ariel R.,Blankert, Sean A.,Halpert, James R.,Nelson, Wendel L.,Isoherranen, Nina
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p. 42223 - 42232
(2013/02/22)
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- A sensitive and specific method for measurement of multiple retinoids in human serum with UHPLC-MS/MS
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Retinol (vitamin A) circulates at 1-4 μM concentration and is easily measured in serum. However, retinol is biologically inactive. Its metabolite, retinoic acid (RA), is believed to be responsible for biological effects of vitamin A, and hence the measurement of retinol concentrations is of limited value. A UHPLC-MS/MS method using isotope-labeled internal standards was developed and validated for quantitative analysis of endogenous RA isomers and metabolites. The method was used to measure retinoids in serum samples from 20 healthy men. In the fed state, the measured concentrations were 3.1 ± 0.2 nM for at RA, 0.1 ± 0.02 nM for 9-cisRA, 5.3 ± 1.3 nM for 13-cisRA, 0.4 ± 0.4 nM for 9,13-dicisRA, and 17.2 ± 6.8 nM for 4oxo-13-cisRA. The concentrations of the retinoids were not significantly different when measured after an overnight fast (3.0 ± 0.1 nM for atRA, 0.09 ± 0.01nM for 9-cisRA, 3.9 ± 0.2 nM for 13-cisRA, 0.3 ± 0.1 nM for 9,13-dicisRA, and 11.9 ± 1.6 nM for 4oxo-13-cisRA). 11-cisRA and 4OH-RA were not detected in human serum. The high sensitivity of the MS/MS method combined with the UHPLC separation power allowed detection of endogenous 9-cis RA and 4oxo-atRA for the first time in human serum. Copyright
- Arnold, Samuel L. M.,Amory, John K.,Walsh, Thomas J.,Isoherranen, Nina
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experimental part
p. 587 - 598
(2012/05/31)
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- All-Trans-Retinol: All-Trans-13,14-Dihydroretinol Saturase and Methods of Its Use
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Compositions of all-trans-retinol: all-trans-13,14-dihydroretinal saturase and methods of use thereof are provided.
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- SYNTHESYS OF THE MAJOR METABOLITES OF (2E,4E,6E,8E)- AND (2Z,4E,6E,8E)-3,7-DIMETHYL-9-(2,6,6,-TRIMETHYL-1-CYCLOHEXEN-1-YL)-2,4,6,8-MONOTETRAENOIC ACIDS (RETINOIC ACID AND 13-cis-RETINOIC ACID)
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Wittig condensation of (2E,4E)-triphenylphosphonium bromide with ethyl formylcrotonate or 4-hydroxy-3-methylbutenolide gives, respectively, the (all-E) and (2Z,4Z)-3,7-dimethyl-9-(2,6,6-trimethyl-3-oxo-1-cyclohexen-1-yl)-2,4,6,8-nonatetraenoic acids.These are converted to oxo and hydroxy metabolites of retinoic acid and 13-cis-retinoic acid.
- Aig, Edward,Focella, Antonino,Parrish, David R.,Rosenberger, Michael,Scott, John W.,Zenchoff, Gladys B.
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p. 419 - 430
(2007/10/02)
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