Characterisation of NagA and NagB from methicillin-resistant Staphylococcus aureus.

by James Sandwell Davies

Institution: University of Canterbury
Year: 2017
Posted: 02/01/2018
Record ID: 2198300
Full text PDF: http://hdl.handle.net/10092/13607


The principal aim of this thesis is to build an understanding of how amino sugars aremetabolised in a clinically relevant strain of Staphylococcus aureus. Amino sugars, such assialic acid and N-acetylglucosamine, are prevalent mucosal sugars that are incorporated intoglycoconjugates attached to mucosal cell surfaces. Specifically, the amino sugars can bescavenged from host glycoconjugates and metabolised by bacterial pathogens as a nutrientsource. Staphylococcus aureus possesses the enzymatic machinery to scavenge host-derivedhost-derived amino sugars from their surrounding environment and utilise them as sources,of carbon, nitrogen and cell wall precursors.A number of amino sugar metabolic pathways converge upon two enzymes, Nacetylglucosamine-6-phosphate deacetylase, NagA, and glucosamine-6-phosphatedeaminase, NagB. These enzymes catalyse the utilisation steps of these pathways, directingmetabolites into either peptidoglycan biosynthesis or glycolysis. Due to this central role in themetabolism of host-derived nutrients, understanding of the structure, function and anypatterns for regulation of these enzymes will inform the development of new antibiotic andtherapeutic strategies.The structure and function of NagA and NagB from methicillin-resistant S. aureus wereinvestigated in this thesis. This constitutes the first biophysical characterisation of theseenzymes from S. aureus. Structural data show that both of these enzymes adopt a dimericarchitecture in solution, which is a novel arrangement in the case of NagB. Kinetic analysesdetail the catalytic capabilities of both enzymes, and suggest two different patterns ofregulation that may influence the activity of these enzymes in vivo.Overall, these experiments add to the understanding of how amino sugars are utilised by S.aureus, and provide a basis for further research into NagA and NagB structure, function andregulation.