Lysozyme molecule. Computer graphic of the molecular structure of the lysozyme molecule. Lysozyme is an anti-bacterial enzyme widely distributed in human body fluids and secretions such as tears or saliva. It targets a protein in the cell walls of bacteria, causing them to burst open and die. The atoms are colour-coded: carbon (grey), oxygen (red), nitrogen (blue) and sulphur (yellow). Sheets (light blue) and helical regions (orange) show the complex structure of the amino acid backbone of the enzyme.