- Substrate specificity and inhibitor sensitivity of rabbit 20α-hydroxysteroid dehydrogenase
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In this study, we examined the substrate specificity and inhibitor sensitivity of rabbit 20α-hydroxysteroid dehydrogenase (AKR1C5), which plays a role in the termination of pregnancy by progesterone inactivation. AKR1C5 moderately reduced the 3-keto group of only 5α-dihydrosteroids with 17β- or 20α/β-hydroxy group among 3-ketosteroids. In contrast, the enzyme reversibly and efficiently catalyzed the reduction of various 17- and 20-ketosteroids, including estrogen precursors (dehydroepiandrosterone, estrone and 5α-androstan-3β- ol-17-one) and tocolytic 5β-pregnane-3,20- dione. In addition to the progesterone inactivation, the formation of estrogens and metabolism of the tocolytic steroid by AKR1C5 may be related to its role in rabbit parturition. AKR1C5 also reduced various non-steroidal carbonyl compounds, including isatin, an antagonist of the C-type natriuretic peptide receptor, and 4-oxo-2-nonenal, suggesting its roles in controlling the bioactive isatin and detoxification of cytotoxic aldehydes. AKR1C5 was potently and competitively inhibited by flavonoids such as kaempferol and quercetin, suggesting that its activity is affected by ingested flavonoids.
- Endo, Satoshi,Arai, Yuki,Hara, Akira,Kitade, Yukio,Bunai, Yasuo,El-Kabbani, Ossama,Matsunaga, Toshiyuki
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p. 1514 - 1518
(2013/10/08)
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- Rabbit 3-hydroxyhexobarbital dehydrogenase is a NADPH-preferring reductase with broad substrate specificity for ketosteroids, prostaglandin D2, and other endogenous and xenobiotic carbonyl compounds
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3-Hydroxyhexobarbital dehydrogenase (3HBD) catalyzes NAD(P) +-linked oxidation of 3-hydroxyhexobarbital into 3-oxohexobarbital. The enzyme has been thought to act as a dehydrogenase for xenobiotic alcohols and some hydroxysteroids, but its physiological function remains unknown. We have purified rabbit 3HBD, isolated its cDNA, and examined its specificity for coenzymes and substrates, reaction directionality and tissue distribution. 3HBD is a member (AKR1C29) of the aldo-keto reductase (AKR) superfamily, and exhibited high preference for NADP(H) over NAD(H) at a physiological pH of 7.4. In the NADPH-linked reduction, 3HBD showed broad substrate specificity for a variety of quinones, ketones and aldehydes, including 3-, 17- and 20-ketosteroids and prostaglandin D2, which were converted to 3α-, 17β- and 20α-hydroxysteroids and 9α,11β- prostaglandin F2, respectively. Especially, α-diketones (such as isatin and diacetyl) and lipid peroxidation-derived aldehydes (such as 4-oxo- and 4-hydroxy-2-nonenals) were excellent substrates showing low Km values (0.1-5.9 μM). In 3HBD-overexpressed cells, 3-oxohexobarbital and 5β-androstan-3α-ol-17-one were metabolized into 3-hydroxyhexobarbital and 5β-androstane-3α,17β-diol, respectively, but the reverse reactions did not proceed. The overexpression of the enzyme in the cells decreased the cytotoxicity of 4-oxo-2-nonenal. The mRNA for 3HBD was ubiquitously expressed in rabbit tissues. The results suggest that 3HBD is an NADPH-preferring reductase, and plays roles in the metabolisms of steroids, prostaglandin D2, carbohydrates and xenobiotics, as well as a defense system, protecting against reactive carbonyl compounds.
- Endo, Satoshi,Matsunaga, Toshiyuki,Matsumoto, Atsuko,Arai, Yuki,Ohno, Satoshi,El-Kabbani, Ossama,Tajima, Kazuo,Bunai, Yasuo,Yamano, Shigeru,Hara, Akira,Kitade, Yukio
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p. 1366 - 1375
(2013/11/19)
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- Stereospecific reduction of 5β-reduced steroids by human ketosteroid reductases of the AKR (aldo-keto reductase) superfamily: Role of AKR1C1-AKR1C4 in the metabolism of testosterone and progesterone via the 5β-reductase pathway
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Active sex hormones such as testosterone and progesterone are metabolized to tetrahydrosteroids in the liver to terminate hormone action. One main metabolic pathway, the 5β-pathway, involves 5β-steroid reductase (AKR1D1, where AKR refers to the aldo-keto reductase superfamily), which catalyses the reduction of the 4-ene structure, and ketosteroid reductases (AKR1C1-AKR1C4), which catalyse the subsequent reduction of the 3-oxo group. The activities of the four human AKR1C enzymes on 5β-dihydrotestosterone, 5β-pregnane-3,20-dione and 20α-hydroxy-5β-pregnan-3-one, the intermediate 5β-dihydrosteroids on the 5β-pathway of testosterone and progesterone metabolism, were investigated. Product characterization by liquid chromatography-MS revealed that the reduction of the 3-oxo group of the three steroids predominantly favoured the formation of the corresponding 3α-hydroxy steroids. The stereochemistry was explained by molecular docking. Kinetic properties of the enzymes identified AKR1C4 as the major enzyme responsible for the hepatic formation of 5β-tetrahydrosteroid of testosterone, but indicated differential routes and roles of human AKR1C for the hepatic formation of 5β-tetrahydrosteroids of progesterone. Comparison of the kinetics of the AKR1C1-AKR1C4-catalysed reactions with those of AKR1D1 suggested that the three intermediate 5β-dihydrosteroids derived from testosterone and progesterone are unlikely to accumulate in liver, and that the identities and levels of 5β-reduced metabolites formed in peripheral tissues will be governed by the local expression of AKR1D1 and AKR1C1-AKR1C3. The Authors Journal compilation 2011 Biochemical Society.
- Jin, Yi,Mesaros, A. Clementina,Blair, Ian A.,Penning, Trevor M.
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supporting information; experimental part
p. 53 - 61
(2012/06/15)
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- A New Chiral Director for the Highly Diastereoselective Borane Reduction of Steroid-20-ones
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The synthesis of a new chiral boroxazolidine was achieved which was used to control the stereochemistry of the borane reduction of the 20-keto group of steroids. The otherwise hardly accessible 20α-(20S)-alcohol can thus be prepared in a yield of 91 percent.
- Goendoes, Gyoergy,Dombi, Gyoergy,Orr, James C.
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p. 1055 - 1060
(2007/10/03)
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- Borane Reduction of the Steroid 20-Ketone Group in the Presence of Various Chiral β-Amino Alcohols
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The direction of reduction of 20-carbonyl group of 3α-hydroxy-5β-pregnan-20-one (1) with a complex of borane-methyl sulfide and chiral β-amino alcohols, depends on the chirality of the amino alcohol.Where there is a 2-phenyl or 2-benzyl substituent, then the S enantiomer gives exclusively the steroid 20R alcohol 3.The R enantiomer of 2-amino-2-phenyl-1-ethanol gives the highest steroid 20S (2) : 20R (3) alcohol ratio. Key Words: 5β-Pregnane, 3α-hydroxy-20-one / Chiral borane reduction / Borane reduction / Steroids
- Goendoes, Gyoergy,Orr, James C.
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p. 581 - 582
(2007/10/02)
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- Mechanism of the D-Homoannulation of Pregnanediol Disulfate in Refluxing 3 N Hydrochloric acid
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In order to elucidate the mechanism of D-homoannulation of pregnanediol 20-sulfate, solvolysis of -5β-pregnane-3α,20α-diol disulfate (3) in refluxing 3 N hydrochloric acid was investigated.The resulting D-homosteroids, 17percenta-methyl-D-homo-5β-androstane-3α,17aβ-diol (8) and 17α-methyl-17aβ-chloro-D-homo-5β-androstan-3α-ol (10), contained a quantitative amount of (13)C only at C-17, indicating that the ring-enlargement reaction of the 20α-ol sulfate proceeded with stereospecific migration of the C16-C17 bond.The same result was obtained from isomeric -5β-pregnane-3α,20β-diol disulfate (6).Based on these results,the D-homoannulation of pregnanediol 20-sulfate was concluded to proceed by a stepwise mechanism through the C-20 carbocation.The stereochemistry of this Wagner-Meerwein type rearrangement reaction is also discussed. Keywords --- 5β-pregnane-3α,20α-diol (pregnanediol); pregnanediol disulfate; 5β-pregnane-3α,20β-diol; D-homoannulation; stereochemistry; steroidal sulfate; acid hydrolysis; (13)C-NMR
- Yoshizawa, Itsuo,Itoh, Shinji,Nagata, Kyoko,Kawahara, Norio
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p. 3819 - 3828
(2007/10/02)
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- METABOLISM AND CONJUGATION OF PROGESTERONE BY BOVINE LIVER AND ADIPOSE TISSUES, IN VITRO
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The ability of bovine liver and fat to metabolize progesterone and also to form glucuronide conjugates with these progestins in vitro was investigated.Tissue supernatants were incubated with progesterone, UDP-glucuronic acid, and a NADPH generating system for 5 hr, at 37 deg C.Steroids were identified by thin-layer chromatography, high performance liquid chromatography, and recrystallization to a constant specific activity.The total original radioactivity which could not be removed by exhaustive ether extraction (presumptive conjugates) was 44.7 +/- 14.2percent in liver, 5.0 +/- 3.6percent in subcutaneous fat, and 3.7 +/- 2.2percent in kidney fat samples.Progestins identified in liver samples include 5β-pregnane-3α,20α-diol (free and conjugate), 5β-pregnane-3α,20β-diol (free and conjugate), 3α-hydroxy-5β-pregnan-20-one (free and conjugate), 3β-hydroxy-5β-pregnan-20-one (free), 5β-pregnane-3,20-dione (free), and progesterone (conjugate).Progestins identified in both the free and conjugate fractions of subcutaneous fat and kidney fat samples include progesterone, 3α-hydroxy-5β-pregnan-20-one, 20β-hydroxy-4-pregnen-3-one, and 20α-hydroxy-4-pregnen-3-one.Differences due to sex of bovine used were noted.These results confirm the ability of bovine liver to readily metabolize progesterone and form glucuronide conjugates of these compounds and suggest that adipose tissues take an active role in these actions in cattle.
- Clemens, J. D.,Estergreen, V. L.
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p. 287 - 306
(2007/10/02)
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- Stereoselective and Regioselective Reduction of Steroid Ketones by Potassium Tri(R,S)-s-butyl)borohydride
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Potassium tri(R,S-s-butyl)borohydride reduces 3-oxo-steroids of the 5α- and 5β-series to the axial alcohol under conditions in which the 17- and 20-ketone groups remain unaffected.
- Goendoes, Gyoergy,Orr, James C.
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p. 1239 - 1240
(2007/10/02)
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- Clinical Analysis on Steroids. XII. Occurrence of D-Homoannulation during the Hot Acid Hydrolysis of 5β-Pregnane-3α,20α-diol Disulfate
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Two D-homosteroids were isolated from the hydrolyzate of 5β-pregnane-3α,20α-diol disulfate (II) when it was refluxed in 3N hydrochloric acid.The structures of these steroids have been elucidated as 17α-methyl-D-homo-5β-androstane-3α,17aβ-diol (VI) and 17α-methyl-17aβ-chloro-D-homo-5β-androstan-3α-ol (VIII) by instrumental analyses.The former was identical with a synthetic specimen derived from 5β-pregnane-3α,20β-diol disulfate (IV) by uranediol rearrangement.The main hydrolyzates obtained were 17α-ethyl-17β-methyl-18-nor-5β-androst-13-en-3α-ol (V) and 5β-pregnane-3α-20α-diol (III).
- Yoshizawa, Itsuo,Nagata, Kyoko,Oh'uchi, Ryoko,Itoh, Shinji,Kanaiwa, Yoshio,Amiya, Takashi
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