Dr. Myles Poulin
University of Maryland – Department of Chemistry and Biochemistry
Friday, April 23, 2021
HOST: Dr. Songon An
“Chemical and biochemical approaches to probe substrate recognition by biofilm degrading glycosidase enzymes”
Infections by biofilm forming bacteria continue to be a major health challenge costing an estimated additional $11 billion in health care costs in the USA annually. Bacterial biofilms consist of surface attached bacteria encased in an extracellular polymeric substance (EPS) composed of exported polysaccharides, proteins and extracellular DNA that facilitates both cell–cell and cell–surface attachment, and serves as a protective barrier for the encased cells. The breakdown of biofilm EPS components using enzyme bio-catalysts has emerged as a promising strategy to disrupt and treat biofilms. One of the most common biofilm exopolysaccharides consists of partially de-N-acetylated b-(1®6)-poly-N-acetylglucosamine (dPNAG) and is found in the EPS of both gram-positive and gram-negative human pathogens, including Staphylococcus epidermidis and Staphylococcus aureus. There are two enzymes that specifically hydrolyze dPNAG known, and relatively little information about the specific interactions required for substrate recognition and specificity in these enzymes is available. We have used a combination of chemically defined synthetic dPNAG analogs and targeted site-directed mutagenesis to probe the mechanism of substrate recognition by Dispersin B (DspB), a PNAG specific glycosidase. This led to the identification of negatively charged patches that play a role in substrate recognition in DspB both in vitro and in biofilm dispersal. These studies provide new insight into the recognition mechanism for cleavage of deacetylated exopolysaccharides by DspB that can aid in the development of more efficient dPNAG hydrolase enzymes.