对于β-lactams和类似β-sultams与氨酸β-lactamases反应的不同过渡状态结构
Wing Y Tsang1, Naveed Ahmed, Paul S Hinchliffe
1Department of Chemical and Biological Sciences, The University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
Journal of the American Chemical Society
|December 8, 2005
概括
N-acylβ-sultams通过硫化来禁用C类β-乳酸酶,在机理上与β-lactams不同. 这些新型抑制剂在酶反应中显示出不同的过渡状态,为β-乳酸酶抑制提供了洞察力.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 药用化学 医学化学
背景情况:
- β-乳酸胺是关键的抗生素,但由β-乳酸胺酶介导的耐药性需要新的抑制剂.
- β-sultams,β-lactams的硫类相似物,代表了一个潜在的类型的酶抑制剂.
- 来自Enterobacter cloacae P99的C类β-乳酸酶是抗生素耐药性研究的重要目标.
研究的目的:
- 调查N-acylβ-sultams通过何种机制使C类β-乳酸酶失活.
- 为了比较β-sultam硫化与β-lactam酶解的反应动力学和过渡状态.
- 阐明离开组和过渡状态结构在酶抑制中的作用.
主要方法:
- 使用N-acylβ-sultams和N-acylβ-lactams与纯化的C类β-lactamase的酶动力学研究.
- 确定二次速率常数,用于无活化 (k ((i)) 和水解 (kcat/K ((m)).
- 电子喷雾电离质谱法 (ESI-MS) 用于表征反应中间体和产品.
- 分析pH依赖度和Bronstedβ (lg) 值以探测过渡状态特征.
主要成果:
- N-acylβ-sultams作为新型无活化剂,在活性部位形成硫酸.
- 该反应通过C-O键裂变和脱氨的形成进行,与β-乳酸溶解不同.
- 与氧化物催化水解相比,用β-sultams的酶催化反应表现出较晚的过渡状态,表明显著的S-N键裂变.
- 对于β-苏尔塔姆硫化 (-1.46) 的Bronstedβ值与β-乳酸盐水解 (-0.06) 显著不同,突出显示了机制差异.
结论:
- 通过硫化机制,N-acylβ-sultams是C类β-lactamase的有效抑制剂.
- 与β-lactam水解相比,该酶在β-sultam无活化过程中使用了不同的过渡状态.
- 了解这些机制差异可以指导新β-乳糖酶抑制剂的设计.
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