DROSOPHILA ALCOHOL-DEHYDROGENASE - EVALUATION OF SER(139) SITE-DIRECTED MUTANTS

Drosophila alcohol dehydrogenase (DADH) belongs to the large and highl y heterogeneous (15-30% residue identity) short-chain dehydrogenase/re ductase family (SDR), It is the only reported member that oxidizes mai nly ethanol and 2-propanol among other alcohols. To confirm the role o f Ser(139) we constructed two site-directed mutants, Ser(139)Ala and S er(139)Cys, which show no enzymatic activity. Molecular replacement an d data from crystallographically refined 3D structures confirm the pos ition of Ser(139), whose hydroxyl group faces the cleft of the presume d catalytic pocket, very close to Tyr(152) and Lys(156). Thus, consist ent with the constitution of the catalytic triad of other SDR, our res ults suggest that Ser(139) of DADH is directly involved in the catalyt ic reaction. (C) 1997 Federation of European Biochemical Societies.