The Rhodococcus erythropolis DCL14 limonene‐1,2‐epoxide hydrolase gene encodes an enzyme belonging to a novel class of epoxide hydrolases

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Abstract
Recently, we reported the purification of the novel enzyme limonene‐1,2‐epoxide hydrolase involved in limonene degradation by Rhodococcus erythropolis DCL14. The N‐terminal amino acid sequence of the purified enzyme was used to design two degenerate primers at the beginning and the end of the 50 amino acids long stretch. Subsequently, the complete limonene‐1,2‐epoxide hydrolase gene (limA) was isolated from a genomic library of R. erythropolis DCL14 using a combination of PCR and colony hybridization. The limA gene encoded a 149‐residue polypeptide with a deduced molecular mass of 16.5 kDa. It was functionally expressed in Escherichia coli. The amino acid sequence of limA contains neither any of the conserved regions of the α,β‐hydrolase fold enzymes, to which most of the previously reported epoxide hydrolases belong, nor any of the conserved motifs present in leukotriene A4 hydrolase. The structural data presented in this paper confirm previous physical and biochemical findings [van der Werf et al. (1998) J. Bacteriol. 180, 5052–5057] that limonene‐1,2‐epoxide hydrolase is the first member of a new class of epoxide hydrolases.