Bacteriophage phi11 lysin: Physicochemical characterization and comparison with phage phi80α lysin

• A physicochemical investigation of lysins of phages phi11 and phi80α was carried out.
• Me++ ions and cysteine residues maintain the active conformation of phage phi11 lysin.
• Lysin of phage phi11 is much more stable than lysin of phage phi80α.
• Schemes of inactivation of lysins of phages phi11 and phi80α are suggested.

Phage lytic enzymes are promising antimicrobial agents. Lysins of phages phi11 (LysPhi11) and phi80α (LysPhi80α) can lyse (destroy) cells of antibiotic-resistant strains of Staphylococcus aureus. Stability of enzymes is one of the parameters making their practical use possible. The objectives of the study were to investigate the stability of lysins of phages phi11 and phi80α in storage and functioning conditions, to identify optimum storage conditions and causes of inactivation. Stability of the recombinant LysPhi11 and LysPhi80α was studied using turbidimetry. CD-spectroscopy, dynamic light scattering, and electrophoresis were used to identify causes of inactivation. At 37 °C, pH 7.5 and concentration of NaCl not higher than 150 mM, LysPhi11 molecules contain a high percentage of random coils (43%). However, in spite of this the enzyme has high activity (0.4–0.8 OD600 nm s−1 mg−1). In storage conditions (4 °C and 22 °C, pH 6.0–9.0, 10–500 mM NaCl) LysPhi11 is inactivated by a monomolecular mechanism. The optimum storage conditions for LysPhi11 (4 °C, pH 6.0–7.5, 10 mM NaCl) were selected under which the time of the enzyme half-inactivation is 120–160 days. LysPhi80α stability is insufficient: at 37 °C the enzyme loses half of its activity almost immediately; at 4 °C and 22 °C the time of half-inactivation of LysPhi80α varies in the range from several hours to 3 days. Despite the common properties in the manifestation of antistaphylococcal activity the kinetic behavior of the enzymes is different. LysPhi11 is a more promising candidate to be used as an antimicrobial agent.