Construction and characterization of hybrid dehydratases between adenosylcobalamin-dependent diol and glycerol dehydratases

Adenosylcobalamin-dependent diol dehydratase and glycerol dehydratase are isofunctional enzymes that catalyze the dehydration of 1,2-diols to the corresponding aldehydes. Although they bear different metabolic roles, both enzymes consist of three different subunits and possess a common (αβγ)₂ structure. To elucidate the roles of each subunit, we constructed expression plasmids for the hybrid dehydratases between diol dehydratase of Klebsiella oxytoca and glycerol dehydratase of Klebsiella pneumoniae in all the combinations of subunits by gene engineering techniques. All of the hybrid enzymes were produced in Escherichia coli at high levels, but only two hybrid enzymes consisting of the α subunit from glycerol dehydratase and the β subunits from diol dehydratase showed high activity. The substrate specificity, the susceptibility to inactivation by glycerol, and the monovalent cation specificity of the wild type and hybrid enzymes were primarily determined by the origin of their α subunits.