Аннотация:Staphylococcus aureus is one of the most dangerous pathogens, because almost 90% of its strains are multi-drug resistant. In this regard, it is necessary to develop alternative methods of S. aureus infections treatment, phage lysins (enzymes produced by phages for lysis of bacterial cell walls) are the most perspective. In 2005, enzyme LysK was isolated; this biocatalyst is active towards to a broad spectrum of Staphylococcus aureus strains, including ones resistant to methicillin and vancomycin.
The main difficulty for application of LysK in medicine is its low stability at storage (4, 22ºC) and functioning (37ºC) temperatures, due to the aggregation of enzyme molecules. The effective way to suppress protein-protein interactions is the usage of charged polymers.
In this study we investigated the influence of positively charged block-copolymers PLLa-PEGb (a=10, 30; b=23, 114) on stability of LysK enzyme at different polymer’s concentrations (1-100 charge excess of block-ionomer in relation to enzyme), temperatures (4, 22, 37°С) and concentrations of low-molecular weight electrolyte (11, 150, 300, and 500 mM NaCl).
We showed that the addition of block-copolymers to LysK increased its stability under all the above temperatures. As a quantitative criterion of stability the value of half-inactivation time was selected. Thus, at PLL30-PEG114/LysK charge ratio 10:1 at the temperature of 22ºС half-inactivation time increased from 2 to 25 days, and at the temperature of 37ºС - from 0.5 to 100 hours. Dynamic light scattering method confirmed the formation of complexes between the molecules of the enzyme and block-copolymers, due to which, apparently, the stabilizing effect was achieved.
The work was supported by project of Russian Federation Ministry of Education 11.G34.31.0004 and SkolTech N 182-MRA.