Development of Novel Lyases and Their Application to the Synthesis of Optically Active Compounds

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First, we screened for microorganisms having new hydro-lyases catalyzing hydration of maleic acid and itaconic acid, respectively, to produce D-malic acid and citramalic acid which are food additives and starting materials in synthetic organic chemistry, etc. The bacterial maleate hydratase from Arthrobacter sp. was purified to homogeneity and characterized. The culture and reaction conditions for the production of optically pure D-malate from maleate were studied. Under an optimum condition, 87 grams/liter of D-malate was produced in 20 h. The yield was 72 mole %. (S)-(+)-Citramalate producing activity from itaconate was also studied. A.denitrificans produced (S)-(+)-Citramalate in a 99.9 % enantiomeric excess. Under an optimum condition, 27 g of (S)-(+)-citramalate per liter was produced in 30 h. The yield was 69 mol%.Second, a screening was carried out for new 3-methylaspartate ammonia-lyases which catalyze the synthesis of L-aspartic acid derivatives from fumaric acid derivatives. We discovered for the first time that 3-methylaspartate ammonia-lyase (MAL) producers are relatively widely distributed in the family of facultatively anaerobic Enterobacteriaceae. Crystalline MALs from Citrobacter freundii, C.amalonaticus, and Morganella morganii, were characterized. Using cell-free extracts of the isolates, optically pure (2S, 3S)-3-methylaspartic, (2S, 3S)-3-ethylaspartic, and (2R, 3S)-3-chloroaspartic acids were synthesized from corresponding fumaric acid derivatives.