Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Matsuura, K. et al.

Identification of amino acid residues responsible for differences in substrate specificity and inhibitor sensitivity between two human liver dihydrodiol dehydrogenase isoenzymes by site-directed mutagenesis.

Human liver dihydrodiol dehydrogenase isoenzymes (DD1 and DD2), in which only seven amino acid residues are substituted, differ remarkably in specificity for steroidal substrates and inhibitor sensitivity: DD1 shows 20alpha-hydroxysteroid dehydrogenase activity and sensitivity to 1,10-phenanthroline, whereas DD2 oxidizes 3alpha-hydroxysteroids and is highly inhibited by bile acids. In the present study we performed site-directed mutagenesis of the seven residues (Thr-38, Arg-47, Leu-54, Cys-87, Val-151, Arg-170 and Gln-172) of DD1 to the corresponding residues (Val, His, Val, Ser, Met, His and Leu respectively) of DD2. Of the seven mutations, only the replacement of Leu-54 with Val produced an enzyme that had almost the same properties as DD2. No significant changes were observed in the other mutant enzymes. An additional site-directed mutagenesis of Tyr-55 of DD1 to Phe yielded an inactive protein, suggesting the catalytically important role of this residue. Thus a residue at a position before the catalytic Tyr residue might play a key role in determining the orientation of the substrates and inhibitors.[1]

References

Identification of amino acid residues responsible for differences in substrate specificity and inhibitor sensitivity between two human liver dihydrodiol dehydrogenase isoenzymes by site-directed mutagenesis. Matsuura, K., Deyashiki, Y., Sato, K., Ishida, N., Miwa, G., Hara, A. Biochem. J. (1997) [Pubmed]

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