cDNA cloning and characterization of a new human microsomal NAD+-dependent dehydrogenase that oxidizes all-trans-retinol and 3alpha-hydroxysteroids.

We report the cDNA sequence and catalytic properties of a new member of the short chain dehydrogenase/reductase superfamily. The 1134-base pair cDNA isolated from the human liver cDNA library encodes a 317-amino acid protein, retinol dehydrogenase 4 (RoDH-4), which exhibits the strongest similarity with rat all-trans-retinol dehydrogenases RoDH-1, RoDH-2, and RoDH-3, and mouse cis-retinol/androgen dehydrogenase ((1)see: Messenger RNA.
(2)The RNA template for protein synthesis. mRNA is formed by transcription of the template DNA strand, followed by the excision of introns and the joining of exons to form mature mRNA.
(3)Messenger RNA. An RNA molecule that is the product of transcription of a gene, after that molecule has been spliced and polyadenylated, that can be translated into a protein product. See the Figure at NHGRI. See also Central Dogma.

信使核糖核酸，携带遗传信息，在蛋白质合成时充当模板的RNA。它在核糖体上作为蛋白质合成的模板，决定肽链的氨基酸排列顺序。

" data-original-title="MRNA" data-html="true" data-trigger="foucs">mRNA for RoDH-4 is abundant in adult liver, where it is translated into RoDH-4 protein, which is associated with microsomal membranes, as evidenced by Western blot analysis. Significant amounts of RoDH-4 message are detected in fetal liver and lung. Recombinant RoDH-4, expressed in microsomes of Sf9 insect cells using BacoluGold Baculovirus system, oxidizes all-trans-retinol and 13-cis-retinol to corresponding aldehydes and oxidizes the 3alpha-hydroxysteroids androstane-diol and androsterone to dihydrotestosterone and androstanedione, respectively. NAD+ and NADH are the preferred cofactors, with apparent Km values 250-1500 times lower than those for NADP+ and NADPH. All-trans-retinol and 13-cis-retinol inhibit RoDH-4 catalyzed oxidation of androsterone with apparent Ki values of 5.8 and 3.5 microM, respectively. All-trans-retinol bound to cellular retinol-binding protein (type I) exhibits a similar Ki value of 3.6 microM. Unliganded cellular retinol-binding protein has no effect on RoDH activity. Citral and acyclic isoprenoids also act as inhibitors of RoDH-4 activity. Ethanol is not inhibitory. Thus, we have identified and characterized a sterol/retinol-oxidizing short chain dehydrogenase/reductase that prefers NAD+ and recognizes all-trans-retinol as substrate. RoDH-4 can potentially contribute to the biosynthesis of two powerful modulators of gene expression: retinoic acid from retinol and dihydrotestosterone from 3alpha-androstane-diol.

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