"We know that some natural enzymes have detoxifying properties, so we are trying to make them faster, better and cheaper," says Frank M. Raushel, a professor of chemistry who has been working on enzymes for the last 30 years.
Phosphotriesterase is known for its detoxifying properties of chemical warfare agents such as the nerve agents sarin, soman and VX, as well as agricultural insecticides.
To understand how phosphotriesterase rapidly degrades these compounds, Raushel's team and a team led by led by Hazel M. Holden, professor of biochemistry at the University of Wisconsin-Madison, set about to crystallize the enzyme and determine its structure. Their results, reported in the journal Biochemistry, show that the catalytic part of the enzyme - or "active site" - contains two zinc metal ions.
Raushel and his collaborators have also studied the structure of the enzyme when it binds to a compound. The scientists identified three binding pockets, designated as the "small," "large," and "leaving group" subsites.
"The binding pockets are likely responsible for the orientation of the compounds within the active site of the enzyme," Raushel says. "So we have been attempting to change the sizes and shapes of the binding pockets and look at changes in the enzyme selectivity."
Raushel and his team changed some of the building blocks, or "amino acids," of each pocket one at a time, and replaced them with the amino-acid alanine. Fourteen amino acids were changed (six in the small group, four in the large group and four in the leaving group), creating 14 "mutant" enzymes.