Exploring the abundance of oleate hydratases in the genus Rhodococcus-discovery of novel enzymes with complementary substrate scope.

Oleate hydratases (Ohys, EC 4.2.1.53) are a class of enzymes capable of selective water addition reactions to a broad range of unsaturated fatty acids leading to the respective chiral alcohols. Much research was dedicated to improving the applications of existing Ohys as well as to the identification of undescribed Ohys with potentially novel properties. This study focuses on the latter by exploring the genus Rhodococcus for its plenitude of oleate hydratases. Three different Rhodococcus clades showed the presence of oleate hydratases whereby each clade was represented by a specific oleate hydratase family (HFam). Phylogenetic and sequence analyses revealed HFam-specific patterns amongst conserved amino acids. Oleate hydratases from two Rhodococcus strains (HFam 2 and 3) were heterologously expressed in Escherichia coli and their substrate scope investigated. Here, both enzymes showed a complementary behaviour towards sterically demanding and multiple unsaturated fatty acids. Furthermore, this study includes the characterisation of the newly discovered Rhodococcus pyridinivorans Ohy. The steady-state kinetics of R. pyridinivorans Ohy was measured using a novel coupled assay based on the alcohol dehydrogenase and NAD-dependent oxidation of 10-hydroxystearic acid.