Lysozyme. Model of a molecule of lysozyme, an enzyme that was the first to have its structure determined using X-ray crystallography. Lysozyme, also called muramidase or N-aminomuramide glycanhydrolase, is present in secretions such as tears, saliva, mucus and human milk. It attacks bacteria by breaking down their cell walls. The structure of lysozyme was published by D.C. Phillips in 1965 during a lecture at the Royal Institution, London, and was visualised using this model that is preserved in the Institution's museum.