MIT and Harvard University chemists have discovered the structure of an unusual bacterial enzyme that can break down an amino acid found in collagen, which is the most abundant protein in the human body. The enzyme, known as hydroxy-L-proline dehydratase (HypD), has been found in a few hundred species of bacteria that live in the human gut, including Clostridioides difficile. The enzyme performs a novel chemical reaction that dismantles hydroxy-L-proline, the molecule that gives collagen its tough, triple-helix structure. Now that researchers know the structure of the enzyme, they can try to develop drugs that inhibit it. Such a drug could be useful in treating C. difficile infections, which are resistant to many existing antibiotics. "This is very exciting because this enzyme doesn't exist in humans, so it could be a potential target," says Catherine Drennan, PhD, an MIT Professor of Chemistry and Biology and a Howard Hughes Medical Institute Investigator. "If you could potentially inhibit that enzyme, that could be a unique antibiotic." Dr. Drennan and Emily Balskus, PhD, a Professor of Chemistry and Chemical Biology at Harvard University, are the senior authors of the study, which was published online on March 17, 2020 in eLife. The open-access article is titled "Molecular Basis for Catabolism of the Abundant Metabolite Trans-4-Hydroxy-L-Proline by a Microbial Glycyl Radical Enzyme." MIT graduate student Lindsey Backman and former Harvard graduate student Yolanda Huang, PhD, are the lead authors of the study. The HypD enzyme is a member of a large family of proteins called glycyl radical enzymes. These enzymes work in an unusual way, by converting a molecule of glycine, the simplest amino acid, into a radical -- a molecule that has one unpaired electron.
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