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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• 作者：Satoshi Endo ; Toshiyuki Matsunaga ; Atsuko Matsumoto ; Yuki Arai ; Satoshi Ohno ; Ossama El-Kabbani ; Kazuo Tajima ; Yasuo Bunai ; Shigeru Yamano ; Akira Hara ; Yukio Kitade
• 关键词：3HB ; 3-hydroxyhexobarbital ; 3OB ; 3-oxohexobarbital ; 3HBD ; 3-hydroxyhexobarbital dehydrogenase ; AKR ; aldo-keto reductase ; HSD ; hydroxysteroid dehydrogenase ; PG ; prostaglandin ; TBE ; 6-tert-butyl-2 ; 3-epoxy-5-cyclohexene-1 ; 4-dione ; 4R-TBEH ; 6-tert-butyl-2 ; 3-e
• 刊名：Biochemical Pharmacology
• 出版年：2013
• 出版时间：1 November, 2013
• 年：2013
• 卷：86
• 期：9
• 页码：1366-1375
• 全文大小：1244 K

文摘

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 3¦Á-, 17¦Â- and 20¦Á-hydroxysteroids and 9¦Á,11¦Â-prostaglandin F₂, respectively. Especially, ¦Á-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 K_m values (0.1-5.9 ¦ÌM). In 3HBD-overexpressed cells, 3-oxohexobarbital and 5¦Â-androstan-3¦Á-ol-17-one were metabolized into 3-hydroxyhexobarbital and 5¦Â-androstane-3¦Á,17¦Â-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.