Physicochemical characterization of the staphylolytic LysK enzyme in complexes with polycationic polymers as a potent antimicrobial.

Staphylococcus aureus causes many serious visceral, skin, and respiratory diseases. About 90% of its clinical strains are multi-drug resistant, but the use of bacteriophage lytic enzymes offers a viable alternative to antibiotic therapy. LysK, the phage K endolysin, can lyse S. aureus when purified and exposed externally. It has been investigated in its complexes with polycationic polymers (poly-l-lysines (PLLs) of molecular weights 2.5, 9.6, and 55.2 kDa and their block copolymers with polyethylene glycol PLL10-PEG114, PLL30-PEG114, and PLL30-PEG23) as a basis for creating active and stable antimicrobial. Complexing with polycationic PLLs produces a stabilizing effect on LysK due to structure ordering in its molecules and break-down of aggregates as a result of electrostatic interaction. The stability of LysK in the presence of PLL-PEG block copolymers improves by both electrostatic and hydrophobic mechanisms. Complexes of LysK with 2.5, 9.6, 55.2 kDa poly-l-lysines and PLL30-PEG114 have demonstrated sufficient stability at the temperatures of physiological activity (37 °C) and storage (4 °C and 22 °C).