Inhibition of Class D -Lactamases by Diaroyl Phosphates
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- 作者：Sudipta Majumdar ; S. A. Adediran ; Michiyoshi Nukaga ; and R. F. Pratt
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：December 13, 2005
- 年：2005
- 卷：44
- 期：49
- 页码：16121 - 16129
- 全文大小：181K
- 年卷期：v.44,no.49(December 13, 2005)
- ISSN：1520-4995
文摘
The production of 
-lactamases is an important component of bacterial resistance to -lactamantibiotics. These enzymes catalyze the hydrolytic destruction of -lactams. The class D serine -lactamaseshave, in recent years, been expanding in sequence space and substrate spectrum under the challenge ofcurrently dispensed -lactams. Further, the -lactamase inhibitors now employed in medicine are notgenerally effective against class D enzymes. In this paper, we show that diaroyl phosphates are veryeffective inhibitory substrates of these enzymes. Reaction of the OXA-1 -lactamase, a typical class Denzyme, with diaroyl phosphates involves acylation of the active site with departure of an aroyl phosphateleaving group. The interaction of the latter with polar active-site residues is most likely responsible forthe general reactivity of these molecules with the enzyme. The rate of acylation of the OXA-1 -lactamaseby diaroyl phosphates is not greatly affected by the electronic effects of substituents, probably because ofcompensation phenomena, but is greatly enhanced by hydrophobic substituents; the second-order rateconstant for acylation of the OXA-1 -lactamase by bis(4-phenylbenzoyl) phosphate, for example, is 1.1× 107 s-1 M-1. This acylation reactivity correlates with the hydrophobic nature of the -lactam side-chain binding site of class D -lactamases. Deacylation of the enzyme is slow, e.g., 1.24 × 10-3 s-1 forthe above-mentioned phosphate and directly influenced by the electronic effects of substituents. The effectivesteady-state inhibition constants, Ki, 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 -lactamases,represent an intriguing new platform for the design of -lactamase inhibitors.
-lactamases is an important component of bacterial resistance to -lactamantibiotics. These enzymes catalyze the hydrolytic destruction of -lactams. The class D serine -lactamaseshave, in recent years, been expanding in sequence space and substrate spectrum under the challenge ofcurrently dispensed -lactams. Further, the -lactamase inhibitors now employed in medicine are notgenerally effective against class D enzymes. In this paper, we show that diaroyl phosphates are veryeffective inhibitory substrates of these enzymes. Reaction of the OXA-1 -lactamase, a typical class Denzyme, with diaroyl phosphates involves acylation of the active site with departure of an aroyl phosphateleaving group. The interaction of the latter with polar active-site residues is most likely responsible forthe general reactivity of these molecules with the enzyme. The rate of acylation of the OXA-1 -lactamaseby diaroyl phosphates is not greatly affected by the electronic effects of substituents, probably because ofcompensation phenomena, but is greatly enhanced by hydrophobic substituents; the second-order rateconstant for acylation of the OXA-1 -lactamase by bis(4-phenylbenzoyl) phosphate, for example, is 1.1× 107 s-1 M-1. This acylation reactivity correlates with the hydrophobic nature of the -lactam side-chain binding site of class D -lactamases. Deacylation of the enzyme is slow, e.g., 1.24 × 10-3 s-1 forthe above-mentioned phosphate and directly influenced by the electronic effects of substituents. The effectivesteady-state inhibition constants, Ki, 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 -lactamases,represent an intriguing new platform for the design of -lactamase inhibitors.