Length of hydrocarbon chain and antimicrobial action to Gram-negative bacteria of fatty acylated lysozyme

We have previously shown that lysozyme can be converted into a potent bactericidal protein against Escherichia coli by covalent attachment of one of two palmitic acids to its lysyl residues. Here we report the antimicrobial behavior against E. coli K-12 3301 of lysozyme covalently modified with myristic and stearic acids to determine the effect of each type of fatty acid on the bactericidal action of lysozyme. All types of attached fatty acids, including palmitic acid, were able to transform lysozyme into a bactericidal molecule against E. coli, depending on the length and number of each type of fatty acid. Among the monoacylated lysozyme derivatives, the longer the carbon chain of the attached fatty acid, the more potent the bactericidal lysozyme type, providing a good linear correlation. On the other hand, among the diacylated lysozyme derivatives, palmitoylated lysozyme was found to be the most potent bactericidal agent. The binding capacity of purified E. coli lipopolysaccharide to the most potent bactericidal acylated lysozymes was stronger than to nonmodified lysozyme, whereas myristoylated lysozyme exhibited the strongest affinity. Thus, the results indicate that the bactericidal activity of the modified lysozymes could be attributed to their moderately enhanced membrane fusion capabilities