Better substrates for bacterial transglycosylases
Better substrates for bacterial transglycosylases
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DOI：
10.1021/ja010028q
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发表时间：
2001-04-04
影响因子：
15
通讯作者：
Walker, S
中科院分区：
文献类型：
--
作者：
Ye, XY;Lo, MC;Walker, S
近年来，对抗生素的耐药性迅速增加，现在对公共健康构成了威胁。对治疗耐药感染的新抗生素的需求重新引起了人们对基本细菌酶的结构和功能的兴趣。由于许多已知的抗生素通过阻止肽聚糖的合成发挥作用，所以合成细菌细胞膜周围的肽聚糖的酶受到了特别的关注。在这些酶中，细菌转糖基酶(TGase)代表了一些最有希望的靶标。2，3个TGase位于细菌膜的外表面，在那里它们聚合Lipid II(图1)，Lipid II是一种通过55碳十一烯基链固定在膜上的二糖。尽管TGase在几十年前就被首次发现，但人们对其结构和机制还不是很清楚。研究TGase的一些困难与获取和处理Lipid II的问题有关。由于有55个碳链聚集体，使用Lipid II的分析方法必须包括有机溶剂、洗涤剂和其他添加剂。Lipid II只能从细菌膜中少量分离。3A、5的结果可能是可变的，很难确定问题是由酶还是底物引起的。较好的底物有利于TGase的研究。为了寻找更好的TGase底物，我们合成了天然脂类II以及一系列含有不同脂链的类似物。这些化合物已被测试其作为TGase底物的能力。结果表明，细菌TGase对脂链的结构有明显的偏好，但它们不需要55碳十一烯基部分。事实上，我们已经确定了一种脂链较短的化合物，它是一种比天然脂质II更好的TGase底物。我们以前曾报道过合成一种含有10碳香茅烯基链而不是十一碳十一烯基链的脂类I类似物(方案1，7)。这个Lipid I类似物使我们能够提纯活性Murg，它是将Lipid I转化为Lipid的酶
Resistance to antibiotics has been increasing rapidly in recent years and now represents a threat to public health. The need for new antibiotics to treat resistant infections has led to a resurgence of interest in the structure and function of essential bacterial enzymes. The enzymes that synthesize the peptidoglycan layers surrounding bacterial cell membranes have received special attention because many known antibiotics function by blocking peptidoglycan synthesis. 1 Among these enzymes, the bacterial transglycosylases (TGases) represent some of the most promising targets. 2, 3 TGases are located on the external surface of the bacterial membrane where they polymerize Lipid II (Figure 1), a disaccharide anchored to the membrane by a 55 carbon undecaprenyl chain. Although the TGases were first identified decades ago, their structures and mechanisms are not well understood. 3a, 4 Some of the difficulties in studying TGases are related to problems obtaining and handling Lipid II. Because the 55 carbon chain aggregates, assays utilizing Lipid II, which can be isolated only in small quantities from bacterial membranes, must include organic solvents, detergents, and other additives. 3a, 5 Results can be variable, and it is difficult to determine whether problems are due to the enzymes or to the substrate. Better substrates would facilitate the study of TGases. To identify better TGase substrates, we have synthesized natural Lipid II as well as a set of analogues containing different lipid chains. These compounds have been tested for their ability to function as TGase substrates. The results show that bacterial TGases have clear preferences with regard to the structure of the lipid chain, but they do not require the 55 carbon undecaprenyl moiety. In fact, we have identified a compound with a shorter lipid chain that is a much better TGase substrate than natural Lipid II.We have previously reported the synthesis of a Lipid I analogue (Scheme 1, 7) containing a 10 carbon citronellyl chain in place of the undecaprenyl chain. 6-8 This Lipid I analogue allowed us to purify active MurG, the enzyme that converts Lipid I to Lipid