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Figure 4<br />

Amino acids important in cofactor and catalysis in human 11b-hydroxysteroid<br />

dehydrogenase types 1 and 2. (a) 11b-HSD type 1. Preference of 11b-HSD type 1<br />

for NADPH resides in lysine-44 and arginine-66, which have positively charged side<br />

chains that stabilize the binding of the 2'-phosphate on NADPH. These residues also<br />

counteract the repulsive interaction between glutamic acid 69 and the phosphate group.<br />

(b) 11b-HSD type 2. Preference of 11b-HSD type 2 for NAD+ is due to favorable bonds<br />

with aspartic acid-91, serine-92, and threonine-112. Moreover there is a coulombic<br />

repulsion between aspartic acid-91 and NADP+, which destabilizes binding of NADP+<br />

11b-HSD type 2 lacks a near<strong>by</strong> amino acid with a positively charged side chain that<br />

could diminish the repulsive interaction between NADP+ and aspartic acid-91. Also<br />

shown are threonine residues that could hydrogen bond<br />

to nicotinamide's carboxamidemoiety.<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_198.html (2 of 2) [4/5/2004 5:05:32 PM]

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