Inhibition of class D beta-lactamases by diaroyl phosphates.
The production of beta-lactamases is an important component of bacterial resistance to beta-lactam antibiotics. These enzymes catalyze the hydrolytic destruction of beta-lactams. The class D serine beta-lactamases have, in recent years, been expanding in sequence space and substrate spectrum under the challenge of currently dispensed beta-lactams. Further, the beta-lactamase inhibitors now employed in medicine are not generally effective against class D enzymes. In this paper, we show that diaroyl phosphates are very effective inhibitory substrates of these enzymes. Reaction of the OXA-1 beta-lactamase, a typical class D enzyme, with diaroyl phosphates involves acylation of the active site with departure of an aroyl phosphate leaving group. The interaction of the latter with polar active-site residues is most likely responsible for the general reactivity of these molecules with the enzyme. The rate of acylation of the OXA-1 beta-lactamase by diaroyl phosphates is not greatly affected by the electronic effects of substituents, probably because of compensation phenomena, but is greatly enhanced by hydrophobic substituents; the second-order rate constant for acylation of the OXA-1 beta-lactamase by bis(4-phenylbenzoyl) phosphate, for example, is 1.1 x 10(7) s(-)(1) M(-)(1). This acylation reactivity correlates with the hydrophobic nature of the beta-lactam side-chain binding site of class D beta-lactamases. Deacylation of the enzyme is slow, e.g., 1.24 x 10(-)(3) s(-)(1) for the above-mentioned phosphate and directly influenced by the electronic effects of substituents. The effective steady-state inhibition constants, K(i), are nanomolar, e.g., 0.11 nM for the above-mentioned phosphate. The diaroyl phosphates, which have now been shown to be inhibitory substrates of all serine beta-lactamases, represent an intriguing new platform for the design of beta-lactamase inhibitors.
Majumdar
Sudipta
S
Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459, USA.
Adediran
S A
SA
Nukaga
Michiyoshi
M
Pratt
R F
RF
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D001665:Binding Sites; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000378:metabolism
D001426:Bacterial Proteins; D007527:Isoenzymes; D010710:Phosphates; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases