TYR-179 AND LYS-183 ARE ESSENTIAL FOR ENZYMATIC-ACTIVITY OF 11-BETA-HYDROXYSTEROID DEHYDROGENASE

Tyr-179 and Lys-183 are likely to be functionally important residues in 11β-hydroxysteroid dehydrogenase, as thease amino acids are absolutely conserved in all members of the "short chain dehydrogenase" family. We modified these residues by site-directed mutagenesis of rat cDNA and transfected these constructs into CHO cells. A highly but not absolutely conserved residue, Asp-110, was also studied. Mutation of Tyr-179 to Phe or Ser completely abolished enzymatic activity (interconversion of corticosterone and 11-dehydrocorticosterone), as did Lys-183→Arg. Asp-110→Asn affected activity only mildly. Tyr-179 and Lys-183 may be directly involved in the catalytic function of this class of enzymes. © 1992.