Deracemization Reactions Using Amine Oxidases

In order to be able to apply this deracemization method to a wide range of chiral amines, it was essential to identify monoamine oxidase enzymes possessing both 

Recently, in collaboration with scientists at the University of York, the crystal structure of MAO N D5 has been determined at 1.8 A resolution (Fig ure 14.4) [52]. This new structure provides insights into the nature ofthe mutations and their possible effect in terms of determining the substrate specificity of the enzyme. 

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Flafner et al first reported an oxidase-catalyzed deracemization method using amino acids as the substrate and pkDAAOx or LAAOx from Crotalus adamanteus together with sodium borohydride as the chemical reductant in 1971 [42]. A procedure for the successful deracemization of amino acids was previously reported by Soda et al. [43]. They focused on proline and pipecolic acid as substrates for the production of L-enantiomer by deracemization because these substrates formed stable imines rather than unfavorable keto acids in water by DAAOx. However, the enzyme was denatured by the chemical reaction with sodium borohydride. Turner et al developed an effective production method for (R)- or (S)-amino acids and (S)-amines by a deracemization method using milder chemical reducing reagents such as sodium cyanoborohydride and artificial transfer hydrogenase [44,45]. 

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