Palmitoyl Lysozyme-Induced Stabilization of PE (Phosphatidylethanolamine) Liposomes and Their Interaction with Candida albicans1

The interaction with fungal cells of dioleoylphosphatidylethanolamine liposomes coated with palmitoyl lysozyme was investigated using lysozyme as a stabilizer for an unstable bilayer as well as a recognizer for a specific target cell. Lysozyme, which interacts with chitin in the fungal cell wall, lyses chitin and kills the cells, was acylated with N-hydroxysuccinimide ester of palmitic acid (NHSP) and incorporated into the lipid bilayer. Lysozyme was optimally modified when the ratio of NHSP to lysozyme was 15 at pH 8.0. Modification of lysozyme was detected by SDS-PAGE, and its molecular weight was about 1,500 greater than that of the intact lysozyme at the optimal ratio of NHSP to lysozyme. The activity of palmitoyl lysozyme toward glycolchitin was reduced to 35% of that of intact lysozyme. Both lysozyme and palmitoyl lysozyme had antifungal activities, but palmitoyl lysozyme was more effective than intact lysozyme against Candida albicans. The minimal molar ratio of palmitoyl lysozyme to phosphatidylethanolamine required to form stable liposomes was 2.4 x 10(-4), and the optimal ratio was about 2.4 x 10(-3). The percentage survival of cells treated with the inserted palmitoyl lysozyme was lower than that of cells treated with free palmitoyl lysozyme. These findings suggest that palmitoyl lysozyme-incorporated liposomal membrane is more effectively adsorbed by Candida albicans than free palmitoyl lysozyme is.