ИСТИНА

Background and Goal: Despite the long history of research on lysozyme, many unresolved questions remain regarding the regulation of its functioning in the body. Free lysozyme is found in biological fluids. Lysozyme is also part of the lysosomes of immune cells. According to modern concepts, lysozyme can function as an enzyme, an antimicrobial cationic complex, and a regulator of the immune system in various infectious and non-infectious diseases [1]. Lysozyme concentration has the potential to be an important diagnostic parameter in cancer [1]. The ability of lysozyme to oligomerize is a long-known fact, but a description of the process and the conditions of transformation require further study [2]. Recently, it was experimentally shown that depending on the presence of certain low-molecular ligands in the solution and the concentration of the enzyme itself, the antibacterial activity of lysozyme is regulated, which is presumably a manifestation of the supercooperativity of the enzyme and the presence of several binding sites for the low-molecular effector [3, 4]. Methods: The activity of lysozyme on living bacterial cells was measured by the turbidimetric method [5] on a Shimadzu UV-1800 spectrophotometer. The oligomeric composition of the drugs was determined by size exclusion chromatography on an ÄKTA start chromatograph. Escherichia coli and Micrococcus luteus cells were used as model substrates. Results: Oligomeric transitions of the enzyme with changes in antibacterial activity were discovered. The activity and oligomeric composition of lysozyme are affected by environmental conditions (pH), enzyme concentration, as well as the presence of nonionic and ionic surfactants in the medium. Mathematical models have been proposed that make it possible to calculate the dissociation constants of lysozyme protein complexes and the dissociation constants of lysozyme with low-molecular-weight effector ligands. Conclusions: Knowledge of the regulation of lysozyme functions under various conditions can be useful for diagnosing various diseases. This information could also help develop new treatments, including for diseases caused by antibiotic-resistant bacteria. [1] Ragland SA, Criss AK. From bacterial killing to immune modulation: Recent insights into the functions of lyso-zyme. PLoS Pathog 13(9):e1006512, 2017. [2] Zhang RY, Zhang N, Mohri M, Wu L, Eckert T, et al. Nanomedical Relevance of the Intermolecular Interaction Dynamics—Examples from Lysozymes and Insulins. ACS Omega 4(2):4206–4220, 2019. [3] Shnitko AV., Chernysheva MG, Levashov PA, Badun GA. Kinetic analysis as an approach to studying specific features of lysozyme—pluronic complexes. Russ Chem Bull 70:1400–1403, 2021. [4] Lu WJ, Smirnov SA, Levashov PA. General characteristics of the influence of surfactants on the bacteriolytic activity of lysozyme based on the example of enzymatic lysis of Lactobacillus plantarum cells in the presence of Tween 21 and SDS. BBRC 575:73–77, 2021. [5] Levashov PA, Sedov SA, Shipovskov S, Belogurova NG, Levashov AV. Quantitative Turbidimetric Assay of Enzymatic Gram-Negative Bacteria Lysis. Anal Chem 82(5):2161–2163, 2010.