New Function of Halohydrin Epoxidase and Its Application of the Synthesis of Chiral Building Block.

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We investigated the microbial production of (R)-3-chloro-1,2-propanediol (MCP) from prochiral 1,3-dichloro-2-propanol (DCP) and enzymes involved in the transformation of DCP into (R)-MCP.Microorganisms which utilize MCP or epichlorohydrin (ECH) as a sole carbon source were isolated from soil samples by means of an enrichment culture technique. The production of (R)-MCP from DCP was examined with one of these strains, Corynebacterium sp.strain N-1074. The optical purity of (R)-MCP formed was improved by keeping the level of DCP in the reaction mixture at a low concentration. (R)-MCP was obtained from 77.5 mM DCP with a 97.3% molar conversion yield and an 83.8% e.e.of its optical purity by periodic feeding of the substrate. During the course of the transformation of DCP into (R)-MCP with the cell extract of Corynebacterium sp.strain N-1074, ECH was transiently formed. The cell extract was fractionated into two DCP-dechlorinating activities and two ECH-hydrolyzing activities. Each enzyme was purified and characterized. DCP-dechlorinating activities and two ECH-hydrolyzing activities were proved to be halohydrin hydrogen halide-lyase and epoxide hydrolase, respectively. Each one of them exhibited the sentioselectivity for the conversion of DCP into ECH and ECH into MCP.We also investigated the application of the dehalogenating enzymes catalyzing the interconversion of halohydrins into the corresponding epoxides to the synthesis of beta-hydroxynitriles.