Lysozyme

Lysozyme, also called muramidase (the name lysozyme comes from A. Fleming) is a widely used enzyme that hydrolyses glycosidic bonds between N-acetylmuraminic acid (NAM) and N-acetylglucosamine (NAG) residues in glycoproteins and other macromolecules. Lysozymes are capable of dissolving the cell wall of bacteria by catalyzing the hydrolysis of murein at the glycosidic bond between the N-acetylmuramic acid (NAM) and N-acetylglucosamine moieties. As a result, the bacterial wall is lysed and destroyed.

Lysozymes play an important role as part of the innate immune system in humans and animals. Furthermore, they are found in different functions in plants, fungi and bacteria.

Lysozyme is approved as a food additive under the number E 1105.

Lysozyme is responsible for the antibacterial property of chicken egg white, an effect that has been known for more than 100 years. It is designated as Gal d 4 and is a relevant allergen in chicken white along with the major allergens ovalbumin (Gal d 2) and ovomucoid (Gal d 1) .

30% of chicken egg allergy sufferers are sensitized to lysozyme. This has a practical relevance as lysozyme is widely used e.g. as an antibacterial additive in cheese.

Lysozyme is present in human body fluids for its antibacterial property, such as nasal secretions, saliva and lacrimal fluids. In animals, 3 different types of lysozyme are distinguished (referred to as c-type (chicken or conventional type), g-type (goose type) and called i-type (invertebrate type). Mammals, birds, reptiles, fish produce c-type lysozymes.

Immunohistology: Lysozyme is expressed by monocytes, macrophages, granulocytes, myeloid precursor cells. It serves as an immunohistological marker for histiocytic neoplasia and myeloid leukemia.

Lysozyme is closely related to lactalbumin.

1. Hantschke M et al (2016) Immunohistological techniques. In: L. Cerroni et al. histopathology of the skin. Springer Publishing House Berlin-Heidelberg p. 30.
2. Marseglia A et al (2013) Outcome of oral provocation test in egg-sensitive children receiving semi-fat hard cheese Grana Padano PDO (protected designation of origin) containing, or not, lysozyme. Eur J Nutr 52:877-883.
3. Reese I et al (2015) Allergy to cow's milk and hen's egg: what does molecular allergy diagnostics offer? Allergo J Int 24: 34-41