STRUCTURAL STUDIES ON BETA-LACTAMASE ENZYMES

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 β-内酰胺类抗生素是临床上最常见的抗生素，占全球抗菌药物总消费量的60%以上。它们包括青霉素类、头孢菌素类、单环内酰胺类、青霉烯类和碳青霉烯类，市场上有50多种这类抗生素。60多年来，抗生素的广泛使用和有时不受控制的使用导致了耐药微生物的选择和世界范围内的传播，这对感染性疾病的抗生素治疗构成了严重威胁。细菌对β-内酰胺抗生素的耐药性的主要机制是产生β-内酰胺酶，所述酶水解β-内酰胺的保守四元环，使其失活。 我们目前正在研究两种最近发现的β-内酰胺酶。 第一个，命名为GES-1（圭亚那扩展频谱，以其首次分离的国家命名），最初于2000年描述。 这种ESBL与其他A类β-内酰胺酶的亲缘关系很远，对青霉素类和第一代、第二代和一些第三代头孢菌素（如头孢他啶）产生耐药性，但对单环内酰胺类和碳青霉烯类不产生耐药性。 自2000年以来，已经描述了来自不同地理位置的9种GES型酶（GES-1 - GES-9）。 GES酶家族与TEM和SHV超家族的区别最令人担忧的特征是它们明显能够进化成弱碳青霉烯酶，即能够水解碳青霉烯类抗生素的酶。 第二种酶Oih-1是从日本附近深海泥中发现的一种细菌Oceanobacillus iheyensis中分离出来的。 天然酶已结晶，并通过分子置换确定结构，使用嗜热脂肪芽孢杆菌的β-内酰胺酶作为搜索模型。 冷稳定和嗜温结构的比较分析表明，在Oih-1酶的酸性氨基酸的数量增加，这些残基在分子表面的聚类增加。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Beta-lactams are the most common antibiotics in clinical use and represent more than 60% of total world consumption of antimicrobial drugs. They include penicillins, cephalosporins, monobactams, penems and carbapenems, and over 50 antibiotics of this class are available on the market. Over 60 years of extensive and sometimes uncontrolled use of antibiotics has resulted in selection and world-wide spread of resistant microorganisms, and this poses a serious threat to the antibiotic therapy of infectious diseases. A major mechanism of bacterial resistance to beta-lactam antibiotics is the production of beta-lactamases, enzymes that hydrolyze the conserved four-membered ring of beta-lactams, rendering them inactive. We are currently working on two recently-discovered beta-lactamase enzymes. The first, named GES-1 (Guiana Extended-Spectrum, after the country where it was first isolated) was initially described in 2000. This ESBL is very distantly related to other class A beta-lactamases and produces resistance to penicillins and first- second-, and some third-generation cephalosporins (e.g. ceftazidime) but not to monobactams and carbapenems. Since 2000, nine GES-type enzymes (GES-1 - GES-9) from different geographical locations have been described. The most alarming characteristic of the GES family of enzymes that distinguish them from the TEM and SHV superfamilies, is their apparent ability to evolve into weak carbapenemases, enzymes capable of hydrolyzing carbapenem antibiotics. The second enzyme, Oih-1 was isolated from a bacterium Oceanobacillus iheyensis found in a deep-sea mud near Japan. The native enzyme has been crystallized and the structure was determined by molecular replacement using the beta-lactamase from the mesophilic Bacillus stearothermophilus as the search model. A comparative analysis of the cold-stable and mesophilic structures shows an increased number of acidic amino acids in the Oih-1 enzyme, with a increased clustering of these residues at the molecular surface.