β-Lactamase inhibition by 7-alkylidenecephalosporin sulfones: allylic transposition and formation of an unprecedented stabilized acyl-enzyme.
The inhibition of the class A SHV-1 β-lactamase by 7-(tert-butoxycarbonyl)methylidenecephalosporin sulfone was examined kinetically, spectroscopically, and crystallographically. An 1.14 Å X-ray crystal structure shows that the stable acyl-enzyme, which incorporates an eight-membered ring, is a covalent derivative of Ser70 linked to the 7-carboxy group of 2-H-5,8-dihydro-1,1-dioxo-1,5-thiazocine-4,7-dicarboxylic acid. A cephalosporin-derived enzyme complex of this type is unprecedented, and the rearrangement leading to its formation may offer new possibilities for inhibitor design. The observed acyl-enzyme derives its stability from the resonance stabilization conveyed by the β-aminoacrylate (i.e., vinylogous urethane) functionality as there is relatively little interaction of the eight-membered ring with active site residues. Two mechanistic schemes are proposed, differing in whether, subsequent to acylation of the active site serine and opening of the β-lactam, the resultant dihydrothiazine fragments on its own or is assisted by an adjacent nucleophilic atom, in the form of the carbonyl oxygen of the C7 tert-butyloxycarbonyl group. This compound was also found to be a submicromolar inhibitor of the class C ADC-7 and PDC-3 β-lactamases.
Department of Biochemistry, Case Western Reserve University , 10900 Euclid Ave., Cleveland, Ohio 44106, United States.
Elizabeth A
EA
Rodkey
David C
DC
McLeod
Christopher R
CR
Bethel
Kerri M
KM
Smith
Yan
Y
Xu
Weirui
W
Chai
Tao
T
Che
Paul R
PR
Carey
Robert A
RA
Bonomo
Focco
F
van den Akker
John D
JD
Buynak
D001483:Base Sequence; D002511:Cephalosporins / Q000737:chemistry / Q000494:pharmacology*; D018360:Crystallography, X-Ray; D017931:DNA Primers; D008958:Models, Molecular; D021241:Spectrometry, Mass, Electrospray Ionization; D013450:Sulfones / Q000737:chemistry*; D065093:beta-Lactamase Inhibitors
D002511:Cephalosporins; D017931:DNA Primers; D013450:Sulfones; D065093:beta-Lactamase Inhibitors