AsianScientist (Aug. 16, 2017) – A team led by researchers from the University of Tokyo has found a unique metal ion-containing domain within the three-dimensional structure of an enzyme used by probiotic bacteria to colonize and propagate in our gut. They report their results in the Journal of Biological Chemistry.
Bifidobacteria is a microbe that has attracted significant public interest for its beneficial effects on human health. The bacteria lives in our body without causing harm and possesses several unique metabolic systems to survive in the gut, including the ability to use the sugar chains of mucin—a glycoprotein in the epithelium of the intestinal mucous membrane—as an energy source for growth and development.
In this study, the research group led by Professor Shinya Fushinobu, Assistant Professor Takatoshi Arakawa, and graduate student Mayo Sato of the Graduate School of Agricultural and Life Sciences at the University of Tokyo used X-ray crystallography to reveal the three-dimensional structure of α-N-acetylgalactosaminidase (NagBb), an enzyme that breaks down mucin sugar chains. Bifidobacteria use NagBb to digest the chemical bonds of N-acetylgalactosamine sugars and peptides, splitting them into smaller fragments to be absorbed.
They revealed that the active site in NagBb that recognizes the sugar substrate N-acetylgalactosamine has a metal ion playing a key role in enzymatic activity—thus far, such an N-acetyl sugar-recognition mechanism with a metal ion has not been observed in other similar types of bacterial enzymes.
“Bifidobacteria may have obtained this sort of unique enzyme through molecular evolution arising from the process of symbiosis with humans,” said Fushinobu. “We expect this achievement will lead to the development of a new kind of prebiotics.”
The article can be found at: Sato et al. (2017) The First Crystal Structure of a Family 129 Glycoside Hydrolase from a Probiotic Bacterium Reveals Critical Residues and Metal Co-factors.
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Source: University of Tokyo.
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