An attempt to transform class characteristics within the alcohol dehydrogenase family

Human class I alcohol dehydrogenase was mutated at positions 57 and 115, exchanging for Asp and Arg respectively, in an attempt to introduce glutathione-dependent formaldehyde dehydrogenase characteristics. In addition, class III alcohol dehydrogenase, identical to glutathione-dependent formaldehyde dehydrogenase, was mutated at position 115, introducing Ser or Lys. The attempted class transformation was partly successful considering a higher affinity for 12-hydroxydodecanoate and a lower affinity for ethanol that was monitored for the class I mutant. However, the class I mutant displayed neither glutathione-dependent formaldehyde dehydrogenase activity nor fatty acid activation of alcohol oxidation. Interestingly, both class III mutants showed reduced activities for S-hydroxymethylglutathione and 12-hydroxydodecanoate through increased Km, values. Overall results show that it is not possible, by single point mutations, to completely transform enzyme characteristics between these two classes of alcohol dehydrogenase.