Influence of Different Types of Block Copolymers on the Secondary Structure and Stability of the Staphylolytic Lysk Enzyme

A branched block copolymer of polyethyleneimine and polyethylene glycol (PEI–PEG) and a linear block copolymer of polylysine and polyethylene glycol (PLL–PEG) form complexes with the staphylolytic LysK enzyme. The complexation between LysK and cationic block-copolymers results in a 1.5–2.0-fold increase in the lytic activity of LysK and a 2–20-fold increase in its half-life. The stabilizing effects of the block copolymers depend on the temperature, the NaCl concentration, and the polymer/enzyme ratio. Being an effective stabilizer, linear PLL–PEG provides an increase in the LysK stability suitable for biomedical materials (LysK maintains 100% of its activity after four months at 4°C).