A perstractive enzyme reactor was used for the synthesis of N-(benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (ZAPM), the precursor of the artificial sweetener, aspartame. The synthesis of ZAPM in the reactor proceeded by an enzymatic reaction between N-(benzyloxycarbonyl)-L-aspartic acid (ZA) and L-phenylalanine methyl ester (PM) in the aqueous phase. The synthesized ZAPM in the aqueous phase was mainly extracted into the organic phase, therefore, the concentration of ZAPM in the aqueous phase could be kept low. As a result, high conversion of ZAPM was obtained with this system. The partition coefficients of substances in the aqueous/butyl acetate biphasic system, the mass transfer coefficients of substances through the membrane and the enzymatic kinetics of ZAPM synthesis were determined experimentally. The reaction model which was based on the material mass balance equations was discussed to estimate the performance of the perstractive enzyme reactor system. The calculation values using the model and the experimental data showed good agreement with the concentration changes of the substances in the system.