ENZYME SOLUBILIZATION IN A REVERSED MICELLAR MICROREACTOR WITH A BILE-SALT COSURFACTANT

Spectroscopic techniques (UV absorbance, circular dichroism, fluoresce nce emission and anisotropy, and light scattering) were used to invest igate enzyme solubilization in Aerosol-OT (AOT) reversed micelles in w hich a bile salt, sodium taurocholate (NaTC), is used as a novel cosur factant. NaTC significantly increases the water capacity and size of t he reversed micelles through surfactant reorganization. The solubiliza tion of several enzymes, including lysozyme, chymotrypsin, lipase, lip oxidase, carbonic anhydrase, and ribonuclease A, was demonstrated. The se enzymes, ranging in mass from 10(4) to 10(5) Da, are incorporated i n the micelles in stable, optically transparent solutions. Several oth er proteins were not successfully solubilized. The presence of NaTC in the reversed micelles significantly altered the conformations of the solubilized enzymes, apparently by promoting unfolding of the enzyme t hrough interactions with the interior micellar interface. Lysozyme and lipase respond to solubilization in the AOT/NaTC micelles by altering their conformations to accommodate the micellar structure. The effect of NaTC is greatest far lysozyme, inducing a higher degree of order a nd helicity in the enzyme structure. Chymotrypsin, on the other hand, disrupts the micellar structure and reorganizes the surfactants to acc ommodate its own preferred conformation, Addition of NaTC to the rever sed micelles causes a 3-fold increase in the enzymatic activity of sol ubilized chymotrypsin. (C) 1997 Academic Press.