“Lysozyme (also called muramidase) is an enzyme capable of disrupting bacterial cell walls and is the first enzyme to have its three-dimensional structure determined via X-ray diffraction. To achieve this, crystallized lysozyme was mounted and exposed to a beam of X-rays that are scattered and recorded on film (imaging plates are now used). The result was a diffraction pattern used to generate an electron density map. The electron density map was used to help generate a model of the protein structure.

Lysozyme is found in many organisms, cells, and secretions such chicken egg whites, mammalian neutrophils, human and animal tears, saliva, and mucus. It is also present in human milk, the lungs, kidney and other organs. The widely studied hen egg white (HEW) lysozyme is a 14.4 kilodalton, single 129 amino acid peptide which is folded into a compact globular structure with a cleft on one side. The substrate for this enzyme is a polysaccharide consisting of alternating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), the constituent of bacterial cell walls. Lysozyme catalyzes the cleavage of the β[1-4] glycosidic linkages between N-acetylmuramic acid and N-acetylglucosamine. The arrow in the figure below shows the result of lysozyme catalytic action on the substrate.

The cleft or crevice of lysozyme contains six subsites. Upon substrate binding, physical distortion of one of the sugars of the active site allows successful substrate binding and catalytic activity. However, another important factor in the bond breakage (and the resulting separation of charge in lysozyme) is due to a significant electrostatic field across the active site cleft. The activity of lysozyme is also a function of pH and ionic strength. For example, at pH 8.0, activity is observed with an ionic strength of not more than 10 mM.”
.

---

Find an error? Take a screenshot, email it to us at error@mytestingsolution.com, and we’ll send you $3!