Chitinases as Antibacterial Proteins: A Systematic Review

Chitinases are hydrolases that catalyze the cleavage of the β-1,4-Oglycosidic linkages in chitin, a polysaccharide abundantly found in nature. Chitin is an important structural component of the cell wall of most fungi and the exoskeleton of arthropods, including insects and crustaceans. These enzymes are widespread in the living world, being found in organisms from all three domains of life. Due to their hydrolytic activity on chitin, chitinases have great biotechnological potential in different areas, such as human health, agriculture and food technology. The antifungal, insecticidal and nematicidal effects of many chitinases have been intensively investigated in the scientific literature, aiming to exploit these properties to protect crops against phytopathogenic fungi and insect pests and parasitic nematodes. On the other hand, the effects of chitinases on bacteria have been underexploited, possibly because chitin is not present in bacterial cell walls. The aim of this study was to search the scientific literature for works describing chitinases with antibacterial activity. Three bibliographic databases were searched using the keywords “chitinase” and “antibacterial” as descriptors and the chosen articles were selected according to specific inclusion and exclusion criteria. As a result, we identified only 5 reports wherein 6 purified chitinases have been shown experimentally to have antibacterial activity. Three out of these 6 antibacterial chitinases were shown to be bifunctional enzymes, which have chitinase and lysozyme activity. The possible mechanism of action of these antibacterial chitinases is discussed, highlighting their potential as antibacterial agents.