Novel reversed micelles formulated by sodium dioleylphosphate (SDOLP) has been developed for enzymatic reaction in organic media. Comparison study between sodium bis-(2-ethylhexyl)-sulfosuccinate (Aerosol-OT or AOT) and SDOLP, which was carried out by investigating the reactivity of each reversed micellar system as reaction media for enzymatic transesterification reaction of N-acetyl-1-phenylalanine ethyl ester (APEE) and 1-propanol, leads to the upshot that α-chymotrypsin immobilized within SDOLP reversed micelles can persevere its high catalytic activity in isooctane. The initial reaction rate of the SDOLP reversed micellar system is almost 60 times higher than that in the AOT system. Additional kinetic results, including the Michaelis constant and the maximum reaction rate, reveal that the inner core of the SDOLP reversed micelles provides a better environment for enzymatic reaction than that of the conventional AOT reversed micelles. © 1998 Elsevier Science S.A. All rights reserved.