ИСТИНА

Lysins 2638aR, LysK and chimeric enzymes Ply187AN-KSH3b, K-L are capable of lysing cells of antibiotic–resistant strains of Staphylococcus aureus and can be considered as promising antibacterial agents. In order to successfully use the enzymes in practice it is important to study their kinetic parameters under various conditions and to identify the relationship “secondary structure-stability”. Optimal conditions for the manifestation of activity of lysins 2638aR, LysK, Ply187AN-KSH3b, and K-L were determined (temperature, pH, NaCl concentration). At a storage temperature (4°C), physiological pH level (7.5) and various NaCl concentrations (10-1000 mM), lysins have high half-inactivation times, with the maximum values of 310 days for K-L, 380 days for LysK, 260 days for 2638aR, and 230 days for Ply187AN-KSH3b. For lysins Ply187AN-KSH3b and LysK, the half–inactivation time and the secondary structure do not change with a change in the concentration of NaCl. For lysins 2638aR and K–L an increase in the concentration of NaCl causes disordering in the secondary structure and a change in the half–inactivation time. Under the conditions of functioning (37ºС, 150 mM NaCl, pH 7.5), all lysins are characterized by high half–inactivation times (10–15 hours) and ordered secondary structures. At 40°C or 42.5°C, there is a sharp decrease in the stability of lysins caused by denaturation. Research results can be used in the development of antibacterial drugs.