CONICET | Buscador de Institutos y Recursos Humanos

Lysozyme (Lys) is a wellknown antimicrobial enzyme since it can catalyze the cleavage of the sugar backbone of the peptidoglycan. Lys is most effective against Gram positive bacteria since the peptidoglycan layer is relatively accessible to the enzyme. The Lys propensity for conversion into amyloid-like fibrils in a proper membrane environment was recently reported. Accumulating evidence has strongly suggested that amyloid fibrils of protein or peptide are cytotoxic and can contribute to the bactericidal action of some antibiotic peptides. In the present work, the Lys structural changes induced by membrane binding or by disulfure bound reduction were characterized and correlated with the bactericidal activity of the protein. Lys showed no conformational change after seven days at <metricconverter w:st="on" productid="37ﾰC">37°C</metricconverter>. However, in the presence of acidic membranes, the FTIR spectrum showed significant changes like the appearance of the band located at 1633 cm-1 which indicates the presence of b-sheets structures. This increment is at the expense of the random coil contribution and thus this conformational change could be considered a beta-structuration. The reduction of disulfide bonds showed similar effect on Lys main structure than the acidic membrane binding. Considering that at the present some evidence indicates that not only the catalytic but also the lipid-binding properties of lys may account for its bactericidal action, the ability of beta-structured Lys to alter the membrane and potential permeability membranes was studied. The obtained results suggest that the Lysozyme fibrillation could be responsible for the enhancement of the bactericidal activity of lysozyme against Gram-negative bacteria, which was observed also after partial reduction of its disulfide bonds. These results could acquire relevance in the biotechnological uses of Lys in food preservation

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