Purification, Gene Cloning, and Characterization of a Novel Halohydrin Dehalogenase from Agromyces mediolanus ZJB120203

A novel halohydrin dehalogenase (HHDH), catalyzing the transformation of 1,3-dichloro-2-propanol (1,3-DCP) to epichlorohydrin (ECH), was purified from Agromyces mediolanus ZJB120203. The molecular mass of the enzyme was estimated to be 28 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A 735-bp nucleotide fragment was obtained based on the N-terminal and internal amino acid sequences of the purified HHDH. The gene codes a protein sequence with 244 amino acid residues, and the protein sequence shows high similarity to Hhe A(AD2) (HHDH from Arthrobacter sp. AD2), defined as Hhe A(Am), which is the seventh reported HHDH. Expression of Hhe A(Am) was carried out in Escherichia coli and purification was performed by nickel-affinity chromatography. The recombinant HheA(Am) possessed an optimal pH of 8.5 and an optimal temperature of 50 A degrees C and manifested a K (m) of 4.58 mM and a V (max) of 3.84 mu mol/min(/)mg. The activity of Hhe A(Am) was not significantly affected by metal ions such as Zn2+, Ca2+, Cu2+, and EDTA, but was strongly inhibited by Hg2+ and Ag+. In particular, the Hhe A(Am) exhibits an enantioselectivity for the conversion of prochiral 1,3-DCP to (S)-ECH. The applications of the Hhe A(Am) as a catalyst for asymmetric synthesis are promising.