Enantioselective oxidation of amphetamine by copper-containing quinoprotein amine oxidases from Escherichia coli and Klebsiella oxytoca

The enantioselective properties of copper-containing quinoprotein amine oxidase (EC 1.4.3.6) from Escherichia coli K12 and Klebsiella oxytoca in the kinetic resolution of (R,S)-1-phenyl-2-aminopropane, amphetamine, have been determined. Determination of the enantiomeric ratio, E=(kcat/KM)R/(kcat/KM)S, the ratio of specificity constants for the enantiomeric substrates, can be accomplished in several ways. For practical reasons, we calculated E using non-linear regression analysis of initial rate data obtained at a fixed overall concentration of amphetamine mixtures of chiral composition ranging from 0 to 50% (R)-(−)-amphetamine [Jongejan et al., Recl. Trav. Chim. Pays-Bas 110 (1990) 247]. It is found that both enzymes catalyze the enantioselective oxidation of amphetamine with E-values of sufficient magnitude (E≈15) which may open the possibility for future application of amine oxidase-catalyzed kinetic resolutions of racemic amphetamine. The preference for the (R)-enantiomer of amphetamine is in agreement with the pro-S specificity that has been observed for the conversion of 2-phenylethylamine. Rationalization of this observation, based on the structure of the E. coli amine oxidase, is discussed.