Importance of Position 170 in the Inhibition of GES-Type β-Lactamases by Clavulanic Acid
Importance of Position 170 in the Inhibition of GES-Type β-Lactamases by Clavulanic Acid
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DOI：
10.1128/aac.01292-10
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发表时间：
2011-04-01
影响因子：
4.9
通讯作者：
Vakulenko, Sergei B.
中科院分区：
文献类型：
--
作者：
Frase, Hilary;Toth, Marta;Vakulenko, Sergei B.
细菌对β-内酰胺类抗生素（青霉素类、头孢菌素类、碳青霉烯类等）的耐药性通常是β-内酰胺酶产生的结果。能够转化碳青霉烯类抗生素的β-内酰胺酶的出现引起了极大的关注，因为这些通常被认为是治疗危及生命的感染的最后手段抗生素。GES家族的β-内酰胺酶是超广谱酶，其包括通过位置170处的单个氨基酸取代获得碳青霉烯酶活性的成员。我们研究了临床上重要的β-内酰胺酶抑制剂克拉维酸对GES-1、-2和-5 β-内酰胺酶的抑制作用。虽然GES-1和-5对克拉维酸的抑制敏感，但GES-2显示出最大的敏感性。这是在位置170处具有规范天冬酰胺的唯一变体。与甘氨酸（GES-1）或丝氨酸（GES-5）相反，具有天冬酰胺的酶则导致对克拉维酸的更高亲和力（Ki = 5 = M）、更高的抑制速率常数和更低的分配比（r约为20）。位置170处的天冬酰胺还导致形成稳定的复合物，例如交联物质和水合醛。相反，在位置170处的丝氨酸导致形成长寿命的反式烯胺物质。这些研究提供了新的见解的重要性，在位置170的残基在确定敏感性的GES酶克拉维酸。
Bacterial resistance to beta-lactam antibiotics (penicillins, cephalosporins, carbapenems, etc.) is commonly the result of the production of beta-lactamases. The emergence of beta-lactamases capable of turning over carbapenem antibiotics is of great concern, since these are often considered the last resort antibiotics in the treatment of life-threatening infections. beta-Lactamases of the GES family are extended-spectrum enzymes that include members that have acquired carbapenemase activity through a single amino acid substitution at position 170. We investigated inhibition of the GES-1, -2, and -5 beta-lactamases by the clinically important beta-lactamase inhibitor clavulanic acid. While GES-1 and -5 are susceptible to inhibition by clavulanic acid, GES-2 shows the greatest susceptibility. This is the only variant to possess the canonical asparagine at position 170. The enzyme with asparagine, as opposed to glycine (GES-1) or serine (GES-5), then leads to a higher affinity for clavulanic acid (K-i = 5 = M), a higher rate constant for inhibition, and a lower partition ratio (r approximate to 20). Asparagine at position 170 also results in the formation of stable complexes, such as a cross-linked species and a hydrated aldehyde. In contrast, serine at position 170 leads to formation of a long-lived trans-enamine species. These studies provide new insight into the importance of the residue at position 170 in determining the susceptibility of GES enzymes to clavulanic acid.