Researchers Mutate Enzyme by ‘Directed Evolution’—Lowering Costs and Helping to Lower Cholesterol

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Looking to lower the cost of pharmaceuticals and help make cholesterol medication affordable for commercial manufacturing, a small team of interdisciplinary researchers at the University of California, Los Angeles discovered that mutations of an enzyme found in soil could efficiently solve a problem faced by the pharmaceutical industry.

Serving as natural catalysts for nearly all biochemical reactions, specialized proteins known as enzymes have proven themselves to be powerful tools in the field of pharmaceuticals. Utilized to transform reagents, or alter the shape of other proteins, enzymes serve key roles in the creation and modification of many drugs you see over the counter and in your prescriptions. But their efficiency only knows certain bounds.

Highly efficient for a certain purpose, enzymes are designed almost always with a single function in mind. However, their particular nature can often cause problems in the lab, where efficiency is demanded over precision.

(Photo : UCLA Professor Ken Houk)

However, one group of researchers led by UCLA Professors Ken Houk, Todd Yeates and Yi Tang, have found a way to flip the script on enzymes. Bringing together approaches from biochemistry, inorganic chemistry and chemical engineering, the team found that as with any necessary change in biology, they needed to look towards evolution to solve their problems.

Originally discovered by another research team at UCLA, a natural enzyme named "LovD" harvested from soil mold, proved to be an effective tool in the development of the cholesterol-lowering drug Simvastatin. Used as an inhibitor of cholesterol production, Simvastatin lowers the risk of many cardiovascular disorders that Latino's face such as stroke, heart attacks and even high blood pressure. But the problem lay in the efficiency of "LovD" as used in a commercial setting.

With too low of a yield, and a naturally slow rate of reaction, the enzyme translated into slow production rates higher costs for patients. So UCLA Professor Yi Tang decided to collaborate with a team at Codexis Inc., an industrial developer of enzymes used in the pharmaceutical industry, and used a process called "directed evolution" to mutate the enzyme into something with even greater efficacy.

"Directed evolution is a laboratory technique that mimics the natural evolution process, but in a much more rapid fashion" Tang says.

(Photo : University of California, Los Angeles)

Mutating the amino acid chains that composed the LovD enzyme, after nine generations of directed evolution, the team found that the newly designated "LovD9" enzyme produced Simvastatin 1,000 times more efficiently courtesy of 29 newly developed mutations in the strand. And through further research, the team collectively was able to not only image the enzyme using techniques like X-ray Crystallography, but also find the secret to why their new enzyme worked on such a greater scale.

"This project could not have been completed without four groups coming together to try and solve a problem that is really challenging, by combining their different specialties and techniques" Gonzalo Jiménez-Osés, postdoctoral researcher at UCLA and the paper's primary author, says. "By piecing together this puzzle from biochemical, engineering, structural, and molecular dynamics angles, it was possible to come to a fairly cohesive picture about how the 'directed evolution' process worked in this case."