lizozymy

Lizozymy, commonly known in English as lysozyme, is a small, globular enzyme that catalyzes the hydrolysis of β-(1,4)-glycosidic bonds in peptidoglycan, the main structural component of bacterial cell walls. This activity weakens the cell wall and can lead to lysis, particularly in bacteria with thick peptidoglycan layers. Lysozymes are part of the innate immune system and are found in high concentrations in secretions such as tears, saliva, mucus, milk, and egg white, as well as in certain white blood cells and gut Paneth cells. The best-known form is the c-type lysozyme found in egg white and many animal tissues, with other forms including g-type and i-type lysozymes found across different species.

Discovery and structure: Lysozyme was discovered by Alexander Fleming in 1922. It was later purified and characterized, establishing its role in antimicrobial defense. The enzyme is about 129 amino acids long and weighs roughly 14.3 kDa, stabilized by four disulfide bonds. In the canonical hen egg white lysozyme, the catalytic site includes Glu35 and Asp52, located in a cleft that binds the substrate and facilitates bond hydrolysis.

Types, sources, and applications: c-type lysozymes are widespread in animals; g-type lysozymes occur in birds and some other species; i-type lysozymes are found in invertebrates. Beyond natural defense, lysozyme is used in the food industry as a natural preservative and in molecular biology to lyse bacterial cells for DNA extraction. Some bacteria have evolved inhibitors to counteract lysozyme, illustrating an ongoing evolutionary arms race between host and microbe.

See also: lysozyme, innate immunity, peptidoglycan, egg white.