The First Enzyme Known to Break Silicon-Carbon Bonds

Environmental & Science Education, STEM, Nature of Science, History of Science, Science & Society

Ed Hessler

-- Our enzyme is terrible. It's not a good enzyme, but it shows that it can be done. -- Frances Arnold, 2018 Chemistry Nobel Laureate.

Chemical & Engineering News just reported a story by Bethany Halford, writing for the January 29, 2024 issue. She begins by describing a difficult problem.stating that by "using directed evolution, scientists have created the first enzyme known to break a silicon-carbon bond. The finding could be a preliminary step toward biodegrading volatile methyl siloxanes—chemicals that are made by the megaton each year."

Here are short quote from Halford's essay to whet your appetite.

--Nicholas Sarai who is the first author said "'Part of the reason we embarked on this research was the detrimental effects of siloxanes on biota as well as the environment." He was a Caltech graduate student in Frances Arnold's laboratory when he worked on the project.

"Arnold is known for creating enzymes that can forge new bonds...The work got the attention of scientists at Dow, a major producer of volatile methyl siloxanes, who reached out to Arnold to see if her lab could develop an enzyme that broke Si–C bonds. Arnold and Dow’s Dimitris Katsoulis led the latest project."

 --“'We’ve only been able to demonstrate that chemistry on one methyl group,' Sarai says. He notes that oxidizing a single Si–C bond in a volatile methyl siloxane does not biodegrade the molecule. 'But it is a proof of concept that enzymes are able to do this silicon-carbon bond cleavage.'"

 

--This is a hard problem as Frances Arnold explains “'There are no organosilicons in nature. And that’s why nature doesn’t break them down,'” Arnold says. 'It’s just a bond that nature doesn’t really care about.'”

Halford closes with two comments from siloxane researchers on the finding as well as ideas for further research.

Halford's essay is short and may be read here.