Structure and enzymatic properties of molecular dendronized polymer-enzyme conjugates and their entrapment inside giant vesicles

Macromolecular hybrid structures were prepared in which two types of enzymes, horseradish peroxidase (HRP) and bovine erythrocytes Cu,Zn-superoxide dismutase (SOD), were linked to a fluorescently labeled, polycationic, dendronized polymer (denpol). Two homologous denpols of first and second generation were used and compared, and the activities of HRP and SOD of the conjugates were measured in aqueous solution separately and in combination. In the latter case the efficiency of the two enzymes in catalyzing a two-step cascade reaction was evaluated. Both enzymes in the two types of conjugates were highly active and comparable to free enzymes, although the efficiency of the enzymes bound to the second-generation denpol was significantly lower (up to a factor of 2) than the efficiency of HRP and SOD linked to the first-generation denpol. Both conjugates were analyzed by atomic force microscopy (AFM), confirming the expected increase in object size compared to free denpols and demonstrating the presence of enzyme molecules localized along the denpol chains. Finally, giant phospholipid vesicles with diameters of up to about 20 μm containing in their aqueous interior pool a first-generation denpol-HRP conjugate were prepared. The HRP of the entrapped conjugate was shown to remain active toward externally added, membrane-permeable substrates, an important prerequisite for the development of vesicular multienzyme reaction systems.