<i>O</i>-Aryloxycarbonyl Hydroxamates:  New β-Lactamase Inhibitors That Cross-Link the Active Site

Abstract

O -Aryloxycarbonyl hydroxamates represent a new class of β-lactamase inhibitors. N -Benzyloxycarbonyl- O -(phenoxycarbonyl) hydroxylamine, for example, inactivates the class C Enterobacter cloacae P99 β-lactamase with a rate constant of 6.1 × 10 3 s -1 M -1; approximately two turnover events accompany the inhibition. N -Benzyloxycarbonyl- O -[(3-carboxyphenoxy)carbonyl] hydroxylamine is comparably effective. These compounds also inactivate the class A TEM β-lactamase. A crystal structure of the inactivated AmpC enzyme, another class C β-lactamase, reveals that the active site has become cross-linked by a carbamate bridge spanning Ser64, the active site nucleophile, and Lys315, a conserved active site residue.