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netLibrary - eBook Summary Structure-based Drug Design by ...

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Figure 2<br />

<strong>Structure</strong> of licorice and carbenoxolone. Glycyrrhizic acid, a constituent of<br />

licorice extract, is found in the root of Glycyrrhiza glabra. The glycosidic group at C3 is<br />

cleaved <strong>by</strong> bacteria in the small intestine to form glycyrrhetinic acid, the compound that<br />

inhibits 11β-hydroxysteroid dehydrogenase. Carbenoxolone, a water soluble synthetic<br />

analog of glycyrrhetinic acid, is widely used to regulate 11β-HSD in vitro and in vivo.<br />

Page 194<br />

(Figure 3, Table 1). This was surprising, as one would expect the two 11β-HSDs to be similar because<br />

they recognize the same substrates. Instead, the two 11β-HSDs have less than 20% sequence identity,<br />

after including gaps in the alignment (Table 1). The same degree of sequence divergence is found in the<br />

four 17β-HSDs [6]. This sequence divergence is reflected in differences in their catalytic properties. For<br />

example 11β-hydroxysteroid dehydrogenase-type 1 (11β-HSD-1) is an NADPH-dependent enzyme that<br />

converts cortisone to cortisol, and 11β-hydroxysteroid dehydrogenase-type 2 is an NAD +-dependent<br />

enzyme that oxidizes cortisol to cortisone. The enzyme 17βHSD-1 is an NADPH-dependent enzyme<br />

that converts estrone to estradiol, and 17βHSD-2 is an NAD +-dependent enzyme that oxidizes estradiol<br />

to estrone and testosterone to androstenedione.<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_194.html (1 of 2) [4/5/2004 5:05:06 PM]

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