TEMPERATURE MODULATED SOLUBILITY-ACTIVITY ALTERATIONS FOR POLY(N-ISOPROPYLACRYLAMIDE)-LIPASE CONJUGATES

Chemical modification of proteins by use of functional polymers is exp ected to endow them with new properties without destroying their nativ e functions, thus providing useful materials for application in differ ent fields. We have synthesized poly(N-isopropylacrylamide) [poly(IPAA m)] co-oligomer with N,N-dimethylacrylamide (DMAAm) and reactive end g roups by telomerization of IPAAm. This co-oligomer exhibits a lower cr itical solution temperature (LCST) at 37 degrees C. Using this tempera ture-responsive semitelechelic co-oligomer, we prepared polymer-enzyme conjugates of lipase by covalent coupling via carboxyl end-groups. Th is bioconjugate exhibits a LCST at 37 degrees C, having rapid, reversi ble hydration-dehydration changes due to highly mobile free polymer en d groups. The conjugate retained its native enzymatic activity below t his critical temperature, above which it precipitated and its catalyti c function was shut off. This conjugate can be readily separated from reaction mixtures as a precipitate by simple temperature changes after reaction and reused in cycles without denaturation. Such a modulated system is attractive for application as a novel bioreactor system.