β-Lactamase inhibition by 7-alkylidenecephalosporin sulfones: allylic transposition and formation of an unprecedented stabilized acyl-enzyme

J Am Chem Soc. 2013 Dec 11;135(49):18358-69. doi: 10.1021/ja403598g. Epub 2013 Dec 3.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Base Sequence
  • Cephalosporins / chemistry
  • Cephalosporins / pharmacology*
  • Crystallography, X-Ray
  • DNA Primers
  • Models, Molecular
  • Spectrometry, Mass, Electrospray Ionization
  • Sulfones / chemistry*
  • beta-Lactamase Inhibitors*

Substances

  • Cephalosporins
  • DNA Primers
  • Sulfones
  • beta-Lactamase Inhibitors