Introduction

Lysozyme was discovered in 1922 by Alexander Fleming during his search for medical antibiotics. His method consisted of adding various matter to bacterial cultures, hoping to find those that would slow the bacteria growth. One day, while suffering from a cold, he added a drop of nasal mucus to the culture and found that it killed the bacteria, thus discovering one of our own natural protections against disease. Lysozyme has since been isolated in many other sources, including saliva, viruses, bacteria, plants, insects, and birds. The most easily obtained source of lysozyme is chicken hen-egg-white, from which it is extracted. Chicken hen-egg lysozyme is probably the most studied globular protein, with an enormous scientific literature. Its three-dimensional structure was determined by X-ray crystallography in the 1960s.

Lysozyme is a small enzyme that protects humans from bacterial infection. It attacks the protective cell walls of bacteria, breaking the carbohydrate chains in the walls, thereby destroying the structural integrity of the bacteria cell walls. As a consequence, the bacteria explode from their internal pressure. Due to its ability to kill bacteria, lysozyme has been used in pharmaceutical and food applications for many years. It also has many other functions, including inactivating certain viruses by forming insoluble complexes and directing anti-inflammatory activity.