Mechanistic enzymology of beta-lactam antibiotic resistance mechanisms and target proteins

丝氨酸β-内酰胺酶（SBL）是降解β-内酰胺抗生素的细菌酶（例如，青霉素和头孢菌素），导致抗生素耐药性。我们的研究项目致力于了解SBL的催化机制，并表征SBL如何进化以降解新的β-内酰胺。大多数SBL不能降解碳青霉烯类，这是一类重要的β-内酰胺抗生素，并且碳青霉烯结构的几个特征被认为会干扰SBL催化。然而，近年来，已经鉴定出有效降解碳青霉烯类的新SBL。我们将研究这些SBL碳青霉烯酶如何降解碳青霉烯类，重点是涉及碳青霉烯羟乙基侧链和吡咯啉环的相互作用。结合分子生物学和生物化学技术，我们将使用19 F NMR光谱来研究这些酶的催化机制的动态方面。基于我们最近的工作，我们已经鉴定了可能抑制SBL碳青霉烯酶的碳青霉烯衍生物。我们将测试这些衍生物作为SBL抑制剂，使用19 F NMR来表征这些相互作用的机制细节。除了拟议的机制和抑制研究外，我们还将研究SBL如何进化以产生碳青霉烯酶活性，并测试微生物组和环境样品中编码的假定SBL是否具有碳青霉烯酶活性。我们的研究旨在确定SBL碳青霉烯酶催化的机制，这将有助于开发对SBL催化降解具有抗性的新型β-内酰胺抗生素。我们在这项工作过程中开发的19 F NMR方法将使未来对其他β-内酰胺降解的机理研究成为可能（例如，头孢菌素），并可以很容易地应用于其他酶底物系统。更一般地说，我们提出的研究计划提供了一个很好的模型，用于研究酶如何进化以克服抑制剂，这是农业和兽医学中具有重要经济意义的领域（例如，抗除草剂杂草的进化，感染牲畜的抗除草剂细菌）。详细的机制研究，如本文提出的，被证明是未来抑制剂开发的一个重要考虑因素。除了有利于学术和工业努力专注于抗生素和抑制剂的发展，该研究计划将通过提供8个高素质的人员（1个博士，2个硕士和5个USRA学生）在化学，生物化学和微生物学方面的宝贵和抢手的研究技能，使加拿大科学界受益。这将为未来的加拿大科学领导人提供一个强大的研究基础，使他们能够促进自然科学的未来研究和发展。

Serine beta-lactamases (SBLs) are bacterial enzymes that degrade beta-lactam antibiotics (e.g., penicillins and cephalosporins), contributing to antibiotic resistance. Our research program is dedicated to understanding the catalytic mechanisms of the SBLs, and characterizing how SBLs evolve to degrade new beta-lactams. Most SBLs cannot degrade carbapenems, an important class of beta-lactam antibiotic, and several features of the carbapenem structure are thought to interfere with SBL catalysis. However, in recent years, new SBLs have been identified that efficiently degrade carbapenems. We will investigate how these SBL carbapenemases degrade carbapenems, focusing on interactions involving the carbapenem hydroxyethyl side chain and pyrroline ring. In combination with molecular biology and biochemistry techniques, we will use 19F NMR spectroscopy to study dynamic aspects of the catalytic mechanisms of these enzymes. Based on our recent work, we have identified carbapenem derivatives that are likely to inhibit SBL carbapenemases. We will test these derivatives as SBL inhibitors, using 19F NMR to characterize the mechanistic details of these interactions. In addition to the proposed mechanistic and inhibition studies, we will examine how SBLs might have evolved to develop carbapenemase activity, and test whether putative SBLs encoded in microbiome and environmental samples possess carbapenemase activity. Our research aims to define the mechanisms of SBL carbapenemase catalysis, which will assist the development of new beta-lactam antibiotics that are resistant to SBL-catalyzed degradation. The 19F NMR methods that we develop during the course of this work will enable future mechanistic studies on the degradation of other beta-lactams (e.g., cephalosporins) by SBLs, and can be readily applied to other enzyme-substrate systems. More generally, our proposed research program provides an excellent model for investigating how enzymes evolve to overcome inhibitors, an area of great economic importance in agriculture and veterinary medicine (e.g., evolution of herbicide-resistant weeds, antibiotic-resistant bacteria infecting livestock). Detailed mechanistic studies, such as those proposed herein, are proving to be an essential consideration for future inhibitor development. In addition to benefitting academic and industrial efforts focused on antibiotic and inhibitor development, this research program will benefit the Canadian scientific community by providing 8 highly qualified personnel (1 PhD, 2 MSc, and 5 USRA students) with valuable and sought-after research skills in chemistry, biochemistry and microbiology. This will provide future Canadian scientific leaders with a strong research base from which they can promote future research and development in the natural sciences.