Ylehd, an epoxide hydrolase with promiscuous haloalkane dehalogenase activity from tropical marine yeast Yarrowia lipolytica is induced upon xenobiotic stress.

Recalcitrant environmental pollutants, like bromoorganics and epoxides are hydrolysed with limited substrate specificities by microbial oxygenases, reductases, hydrolases and dehalogenases. Here, we report the identification and characterisation of a protein (XP_504164) from the tropical marine yeast Yarrowia lipolytica NCIM 3589, known to degrade bromoorganics and epoxides. Multiple sequence alignment suggests it belongs to α/β superfamily with conservation of catalytic triad and oxyanion hole motifs. The corresponding gene cloned and protein (Ylehd) expressed in E. coli BL21AI exhibited epoxide hydrolase activity (24 ± 0.7 nmol s mg protein) at pH 8.0 and promiscuous haloalkane dehalogenase (1.5 ± 0.2 nmol s mg protein) at pH 4.5. Recombinant Ylehd catalyses structurally diverse epoxides and bromoorganics with maximum catalytic efficiency (k/K) of 96.56 and 10.1 mM s towards 1,2-Epoxyoctane (EO) and 1-Bromodecane (BD). The expression of Ylehd was highly induced in presence of BD and EO but not in glucose grown cells as studied by immunoblot analyses, q-PCR and activity levels. Immunoelectron microscopy confirmed higher expression in presence of xenobiotics and located it to cytosol. Such inducible nature of Ylehd suggests its physiological role in xenobiotic stress mitigation. This study represents the first functional characterisation of a bifunctional EH/HLD in eukaryotic microbes with broad substrate specificity making it a potential biocatalyst for bioremediation/biosensing of mixed pollutants.