title: Potential transition state analogue inhibitors for the penicillin-binding proteins.
abstract: Penicillin-binding proteins (PBPs) are ubiquitous bacterial enzymes involved in cell wall biosynthesis. The development of new PBP inhibitors is a potentially viable strategy for developing new antibacterial agents. Several potential transition state analogue inhibitors for the PBPs were synthesized, including peptide chloromethyl ketones, trifluoromethyl ketones, aldehydes, and boronic acids. These agents were characterized chemically, stereochemically, and as inhibitors of a set of low molecular mass PBPs: Escherichia coli (EC) PBP 5, Neisseria gonorrhoeae (NG) PBP 3, and NG PBP 4. A peptide boronic acid was the most effective PBP inhibitor in the series, with a preference observed for a d-boroAla-based over an l-boroAla-based inhibitor, as expected given that physiological PBP substrates are based on d-Ala at the cleavage site. The lowest K(I) of 370 nM was obtained for NG PBP 3 inhibition by Boc-l-Lys(Cbz)-d-boroAla (10b). Competitive inhibition was observed for this enzyme-inhibitor pair, as expected for an active site-directed inhibitor. For the three PBPs included in this study, an inverse correlation was observed between the values for log K(I) with 10b and the values for log(k(cat)/K(m)) for activity against the analogous substrate, and K(m)/K(I) ratios were 90, 1900, and 9600 for NG PBP 4, EC PBP 5, and NG PBP 3, respectively. These results demonstrate that peptide boronic acids can be effective transition state analogue inhibitors for the PBPs and provide a basis for the use of these agents as probes of PBP structure, function, and mechanism, as well as a possible basis for the development of new PBP-targeted antibacterial agents.
authors.affiliation: Division of Pharmaceutical Sciences, University of Missouri-Kansas City, 5005 Rockhill Road, Kansas City, Missouri 64110, USA.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Pechenov
authors.forename: Miglena E
authors.initials: ME
authors.lastname: Stefanova
authors.forename: Robert A
authors.initials: RA
authors.lastname: Nicholas
authors.forename: Sridhar
authors.initials: S
authors.lastname: Peddi
authors.forename: William G
authors.initials: WG
authors.lastname: Gutheil
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis; D000590:Amino Acid Chloromethyl Ketones / Q000138:chemical synthesis; D000890:Anti-Infective Agents / Q000138:chemical synthesis; D001426:Bacterial Proteins; D001880:Boranes / Q000138:chemical synthesis; D001897:Boronic Acids / Q000138:chemical synthesis; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry*; D006602:Hexosyltransferases; D007700:Kinetics; D002267:Muramoylpentapeptide Carboxypeptidase / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D009842:Oligopeptides / Q000138:chemical synthesis; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000737:chemistry*; D010458:Peptidyl Transferases; D013379:Substrate Specificity
chemical_list: D000447:Aldehydes; D000590:Amino Acid Chloromethyl Ketones; D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D001880:Boranes; D001897:Boronic Acids; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase