Substrate specificity and kinetic characterization of peptidoglycan O-acetyltransferase B from Neisseria gonorrhoeae [Microbiology]

May 2nd, 2014 by Moynihan, P. J., Clarke, A. J.

The O-acetylation of the essential cell wall polymer peptidoglycan is a major virulence factor identified in many bacteria, both Gram positive and Gram negative, including Staphylococcus aureus, Bacillus anthracis, Neisseria gonorrhoeae and N. meningitidis. With Gram-negative bacteria, the translocation of acetate from the cytoplasm is performed by an integral membrane protein, PatA, for its transfer to peptidoglycan by O-acetyltransferase PatB, whereas a single bimodal membrane protein, OatA, appears to catalyze both reactions of the process in Gram-positive bacteria. Only phenotypic evidence existed in support of these pathways because no in vitro biochemical assay was available for their analysis which reflected the complexities of investigating integral membrane proteins that act on a totally insoluble and heterogenous substrate such as peptidoglycan. In this study, we present the first biochemical and kinetic analysis of a peptidoglycan O-acetyltransferase using PatB from N. gonorrhoeae as the model system. The enzyme has specificity for muropeptides that possess tri- and tetra-peptide stems on muramyl residues. With simple chitooligosaccharides as substrates, rates of reaction increase with increasing degrees of polymerization to 5/6. This information will be valuable for the identification and development of peptidoglycan O-acetyltransferase inhibitors which could represent potential leads to novel classes of antibiotics.