Enzyme in tears devours bacteria

Alexander Fleming discovered the lysozyme, which is an enzyme that is abundant in tears, saliva, human milk and mucus, back in 1923. The lysozyme defends us against bacterial attacks by catalyzing the hydrolysis of the glycosidic bonds in the polysaccharide found in bacterial cell walls.

Ever since Fleming discovered this enzyme, scientists around the world have been trying understand how this protein actually works. Gregory Weiss, a molecular biologist, and Philip Collins, an associate professor of physics and astronomy at the University of California at Irvine, seem to have finally figured out the secret.

In a recent study published in the journal Science, researchers used a nano-scaled electronic circuit to monitor the dynamics of single molecule of T4 lysozyme. Scientists developed a nano-scaled field-effect transistor by attaching a single molecule of T4 lysozyme to the single-walled carbon nanotubes.

The device would first pick up changes in electrostatic potential created by the enzyme's molecular motion, and then convert and amplify them into dynamically changing electron fluxes. This allowed researchers to listen to the enzyme as it devoured bacteria.

This novel experimental technique, with its advantageous bandwidth and reduced noise, lets researchers overcome the limitations of other common techniques, such as using fluorescence to analyze the dynamics of single molecule.

The research team discovered that the Pac-Man-like motion of the lysozyme enabled it to chomp its way through bacteria. It was not responsive when there were no bacteria around, but it worked at high speed when its favorite food was present.

The researchers were also able to understand how mutations in the enzyme can slow it down, and how surrounding changes made by bacteria can reduce the lysozyme's effectiveness.

According to the results published in the study, a lysozyme undergoes an 8 A?, hinge-like mechanical motion, with two domains closing around the substrate as the lysozyme munches it. In addition, this motion occurs at two different rates: either a slow hinge oscillation of 20 to 90 Hz or a more rapid motion at 200 to 400 Hz, depending on various conditions.

Using the novel approach of single-molecule, researchers were able to understand how the molecular-scaled battle occurs inside our immune system for the first time. Next, their goal is to understand how other more complicated molecules, such as the ones that make us sick or the ones that heal us work.

They believe that this new technique could be of great use in the early detection of cancer and other illnesses. This can subsequently lead to a higher success rate in treating patients with these conditions and may ultimately bring down health care costs.