title: Efficient inhibition of class A and class D beta-lactamases by Michaelis complexes.
abstract: A 6-alkylidiene penam sulfone, SA-1-204, is an efficient inhibitor of both SHV-1 and OXA-1 beta-lactamases with K(I) = 42 +/- 4 nm and 1.0 +/- 0.1 microm, respectively. To gain insight into the reaction chemistry of SA-1-204, the reactions between this inhibitor and SHV-1 and OXA-1 were studied by Raman spectroscopy in single crystals and in solution. Raman signatures characteristic of the unreacted beta-lactam ring show that in both phases the inhibitor binds as a noncovalent Michaelis-like complex. This complex is present as the major population for periods of up to an hour. On longer time scales, the Raman data show that beta-lactam ring opening eventually leads to a complex mixture of reaction products. However, the data clearly demonstrate that the key species for inhibition on the time scale of bacterial half-lives is the noncovalent complex preceding acylation.
authors.affiliation: Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Kalp
authors.forename: Anjaneyulu
authors.initials: A
authors.lastname: Sheri
authors.forename: John D
authors.initials: JD
authors.lastname: Buynak
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Bethel
authors.forename: Robert A
authors.initials: RA
authors.lastname: Bonomo
authors.forename: Paul R
authors.initials: PR
authors.lastname: Carey
mesh_terms: D000215:Acylation; D001665:Binding Sites; D003461:Crystallography; D007700:Kinetics; D012694:Serine; D013059:Spectrum Analysis, Raman; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification
chemical_list: D065093:beta-Lactamase Inhibitors; D012694:Serine; D001618:beta-Lactamases