来自豚鼠诺卡氏菌的A类β-内酰胺酶FAR-1的生化遗传分析及分布
Biochemical-genetic analysis and distribution of FAR-1, a class A beta-lactamase from Nocardia farcinica.
作者信息
Laurent F, Poirel L, Naas T, Chaibi E B, Labia R, Boiron P, Nordmann P
机构信息
Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris, Faculté de Médecine Paris-Sud, 94275 Le Kremlin-Bicêtre Cédex, France.
出版信息
Antimicrob Agents Chemother. 1999 Jul;43(7):1644-50. doi: 10.1128/AAC.43.7.1644.
From genomic DNA of the clinical isolate Nocardia farcinica VIC, a 1. 6-kb Sau3AI fragment was cloned and expressed in Escherichia coli JM109. The recombinant strain expressed a beta-lactamase (pI, 4.6), FAR-1, which conferred high levels of resistance to amoxicillin, piperacillin, ticarcillin, and cephalothin. The hydrolysis constants (kcat, Km, Ki, and 50% inhibitory concentration) confirmed the MIC results and showed that FAR-1 activity is inhibited by clavulanic acid and at a low level by tazobactam and sulbactam. Moreover, FAR-1 beta-lactamase hydrolyzes aztreonam (at a low level) without significant activity against ceftazidime, cefotaxime and imipenem. FAR-1 mature protein of molecular mass ca 32 kDa, has less than 60% amino acid identity with any other class A beta-lactamases, being most closely related to PEN-A from Burkholderia cepacia (52%). A blaFAR-1-like gene was found in all studied N. farcinica strains, underlining the constitutive origin of this gene.
从临床分离株嗜皮诺卡氏菌VIC的基因组DNA中，克隆了一个1.6 kb的Sau3AI片段，并在大肠杆菌JM109中表达。重组菌株表达了一种β-内酰胺酶（pI为4.6），即FAR-1，它赋予了对阿莫西林、哌拉西林、替卡西林和头孢噻吩的高水平抗性。水解常数（kcat、Km、Ki和50%抑制浓度）证实了MIC结果，并表明FAR-1的活性受到克拉维酸的抑制，同时受到他唑巴坦和舒巴坦的低水平抑制。此外，FAR-1β-内酰胺酶可水解氨曲南（水平较低），但对头孢他啶、头孢噻肟和亚胺培南无显著活性。分子量约为32 kDa的FAR-1成熟蛋白与任何其他A类β-内酰胺酶的氨基酸同一性均低于60%，与洋葱伯克霍尔德菌的PEN-A最为密切相关（52%）。在所有研究的嗜皮诺卡氏菌菌株中都发现了一个blaFAR-1样基因，这突出了该基因的组成性起源。
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