Strategies for New Antimicrobial Proteins and Peptides: Lysozyme and Aprotinin as Model Molecules

Abstract

The increasing development of bacterial resistance to traditional antibiotics has reached alarming levels, thus necessitating the strong need to develop new antimicrobial agents. These new antimicrobials should possess both novel modes of action as well as different cellular targets compared with the existing antibiotics. Lysozyme, muramidase, and aprotinin, a protease inhibitor, both exhibit antimicrobial activities against different microorganisms, were chosen as model proteins to develop more potent bactericidal agents with broader antimicrobial specificity. The antibacterial specificity of lysozyme is basically directed against certain Gram-positive bacteria and to a lesser extent against Gram-negative ones, thus its potential use as antimicrobial agent in food and drug systems is hampered. Several strategies were attempted to convert lysozyme to be active in killing Gram-negative bacteria which would be an important contribution for modern biotechnology and medicine. Three strategies were adopted in which membrane-binding hydrophobic domains were introduced to the catalytic function of lysozyme, to enable it to damage the bacterial membrane functions. These successful strategies were based on either equipping the enzyme with a hydrophobic carrier to enable it to penetrate and disrupt the bacterial membrane, or coupling lysozyme with a safe phenolic aldehyde having lethal activity toward bacterial membrane. In a different approach, proteolytically tailored lysozyme and aprotinin have been designed on the basis of modifying the derived peptides to confer the most favorable bactericidal potency and cellular specificity. The results obtained from these strategies show that proteins can be tailored and modelled to achieve particular functions. These approaches introduced, for the first time, a new conceptual utilization of lysozyme and aprotinin, and thus heralded a great opportunity for potential use in drug systems as new antimicrobial agent.

Transfer of egg white proteins with reference to lysozyme during the development ofMeleagris gallopavo(Galliformes: Phasianidae) embryos

“…Alternatively, lysozyme at later stages of development may undergo enzymatic hydrolysis by certain proteases that produce fragments of the enzyme with enhanced activity. It has been shown that the hydrolysis of lysozyme by different proteolytic enzymes, such as clostripain, pepsin and trypsin, caused the exposure of the antibacterial peptides of the enzyme, and as a result increased its antibacterial activity (Pellegrini et al 1997;Ibrahim et al 2001Ibrahim et al , 2002Ibrahim et al , 2005Mine et al 2004).…”

Functional Proteins and Peptides of Hen’s Egg Origin

“…Egg white lysozyme consists of 129 amino acid residues with a molecular weight of 14.4 kDa. Because of its basic character, lysozyme binds to ovomucin, transferrin or ovalbumin in egg white [58]. In nature, lysozyme is found mainly as a monomer but it has been reported to also exist as a reversible dimer, which can be evoked by pH, concentration and/or temperature-dependent phase transition of the molecule.…”

“…Enzymatic hydrolysis of lysozyme is a novel technology that uses proteolytic enzymes for hydrolyzing native lysozyme to produce potent antimicrobial peptides that hidden within its folds. Lysozyme was digested by different proteolytic enzymes, such as clostripain [58,60], pepsin, and trypsin [97,98,99]. All these researchers proved that the resulting peptides lost the enzymatic activities of lysozyme, but exhibited strong bactericidal activities against both Gram-negative (E.coli, Salmonella, Pseudomonas, and Aeromonas) and Gram-positive bacteria (Listeria monocytogenes, Staph aureus, Bacillus spp., and Leuconostics spp.)…”

“…Scanning electron microscopy clearly demonstrated that cell membrane of both Gram-negative and -positive bacteria was damaged by these peptides. Thus these peptides probably have a different mechanism of action than native lysozyme [58,99]. Mine et al (2004) could isolation, purification, and characterization of novel antimicrobial peptides from chicken egg white lysozyme hydrolysate, obtained by peptic digestion and subsequent tryptic digestion.…”

Molecular characterisation, evolution and expression analysis of g-type lysozymes in Ciona intestinalis

“…Gram-negative bacteria, however, are not directly damaged by lysozyme as their outer membrane is significantly coated with lipopolysaccharide (LPS) moieties. Instead, the outer membranes of Gram-negative bacteria must first be disrupted by cationic antimicrobial peptides that expose the inner peptidoglycan layer of bacteria to lysozyme (Banks et al, 1986;Hancock and Scott, 2000;Ibrahim et al, 2002).…”