Enzymatic transformation of -chloroalanine into useful amino acids

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Recent development of chemical synthesis techniques has made it possible to produce <beta>-chloroalanine economically on a large scale. The enzymatic transformation of chemically synthesized <beta>-chloroalanie into useful amino acids was studied. We isolated microorganisms, Bacillus sphaericus L-118 and Pseudomonas putida CR1-1 which are resistant to <beta>-chloro-L-alanine and -chloro-D-alanine, respectively. The formation of O-acetylserine sulfhydrylase of B. sphaericus L-118, was highly enhanced by (beta)-chloro-L-alanine to the medium. The enzyme catalyzes the <beta>-replacement reaction of <beta>-chloroalanine in the presence of sulfide to produce L-cysteine. We optimized the reaction conditions for the enzymatic production of L-cysteine. Under the optimum conditions. 70 g of L-cysteine/L of reaction mixture was produced (conversion yield 80%). In the crude cell extract of P. putida CR 1-1, we found the new enzyme, <beta>-chloro-D-alanine dehydrochlorinase which catalyzes the <beta>-replacement reaction of <beta>-chloro-D-alanine in the presence of sulfide to produce D-cysteine. When various thiol compounds were added instead of sulfide, the corresponding Salkyl-D-cysteine was synthesized. We optimized the reaction conditions to produce D-cysteine. Under the optimal condition, 22.6 g of D-cysteine/L of reaction mixture was produced (conversion yield 100%). D-Cysteine and its derivatives are useful for the production of the semi-synthetic cephalosporin antibiotics.